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(25 Hybridism

Laws of Hybri governing Hybridism The variability of sterility We have as yet must now considered only, as far as can be imperfectly done & chiefly from Gaertner what laws & circumstances regulate the possibility of degrees of fertility with which distinct species unite, & the degrees of fertility of the resultant hybrids. Do they indicate whether species ever covered nets to keep separate The first & perhaps one of the most conspicuous facts is that as we have just seen there is no strong & decided line of demarcation between to species which fertility & inf the species will & will not unite, & between in the fertility of the crossed hybrid offspring;; as might perhaps, a priori, have been expected if the sterility had been simply ordained to prevent the blending of created species. Far from any distinct line of demarcation existing, we find, as has already been incidentally first shown, the most perfect gradation from absolute sterility to perfect fertility, even to fertility to excess as it would appear from Dean Herbert's cases, in excess over the natural fertility. If the pollen of a plant of one Family be placed on the stigma of a species of another family no more result is produced than if so much dust is laid on, & so it is very often is with many clo species much more closely allied, species, even not seldom (Gaertner p. 96) with very many species species of the same genus. The first sign of fertility in evidence of some sexual affinity between two species is the longer persistence of the flower corolla or calyx & of one the flower when dusted & (p. 189 G. Bastard.) p. 68) with the pollen of the other, the other species than if when simply castrated. Even the pollen itself which answer to shown by its protruded behaves differently when laid on the stigma of an allied form (R. Brown) tubes when that same action from what it does when placed on the on

38

(26

not at all allied to it, in which case (Gaertner Bastard p 110) it will not cling to the stigma. A gradation, moreover in the The condition of the pollen (p 19 G.) can be observed in relation to the sexual affinity of the species on the stigma of which it has been placed. So again Gaertner has observed the most curious & gradual se gradation in the slowness (p. 68) of the change colour of withering of the pistil & corolla according to the sexual affinity of the two species experimentised on. We have, also, (p. 102) every gradation of imperfection in the fruit, capsules & seeds: G. has even observed cases in which he has found (p 101) that out of a thousand seeds, which in external appearance were perfect, not one would give germinate. In several certain other instances, the union of two species (p. 138 p. 81) may be tried hundreds of times in vain, & at last one single or a couple two of seeds may be found which germinate & live. Between cases in which a single seed has once or twice only after many years attempts been pursued the cases where the fertility is nearly or even quite perfect, a perfect grad series can be easily perfected. We have seen in an earlier chapter that generally hybrids are more vigorous, hardier, more

39

(26 B Hybridism

not at all allied to it. We next come to cases in which under the most favourable circumstances, of weather, of the time of day & of the year after repeated trials during successive years a single hybrid is reared: & so on by steps to cases in which so nearly a few or quite as many. seed hybrid seed hybrids was come can generally be raised will germinate. are natural seed produced as by natural fertilisation. In an exactly similar manner we have in the hybrids themselves a Sickly Hybrids short-lived ⸮Cases a perfect gradation from extreme sterility to great perfect fertility: even in the most sterile hybrids, (G. (p. 412) & 533) the application of the pollen of either pure parent will generally cause the flower & calyx to endure longer than it otherwise would;* so here in one series the sterility can hardly be considered absolute, though certainly it appears certain that such hybrids never have yielded & probably never would yield seed which Could germinate.

(The simple fact of the a union never having been effected between species of different families & only in a few cases between species of different genera, & that, in closely allied genera between (Herbert. Ammaryll. p 359) Rhododendron, Azalea, Rhodora, between Hippeastrum & Crinum? (Hymenocallis & Ismene Pancratium & Salisbury Herb. Hort. Journ. vol 2, 18. stet ) poor genus.) between Cucubalus, Lychnis, Pancratium & Silene (Gaertner) shows that there is a certain parallelism between systematic affinity & the power capacity of sexual union. So fact already given But this parallelism (p. 121, 168 Gaertner) p 408) is far from closeas has most forcibly shows by experiments. For it has been found impossible to unite cross many species systematically nearly related, as the apple & pear (p. 167 Gaertner); not good examples thus Herbert failed (Hort. Journ vol. 2. p. 82)

39v

Then again Crocus & Narcissus. Even with limit of same genus. familiar Nicotiana, in which the many specs have been now largely crossed. Somewhat similar fact was shewed by Kol. in Digitalis. Herbert shows that 3 Crin, where one at C. capen — Hippeastrum — easily Habranthus

Although we may predicate that forms extremely very remote in our systematic classification certainly will not unite, yet assuredly systematic affinity does not give the Key to the law regulating the fairly fertility of the first cross between any two forms or the fertility of the hybrid offspring. We shall also find this conclusion strongly corroborated when we come to reciprocal crosses.—

Herbert believes that the difficulty in effecting a cross depends on some constitutional differences that effects the species; if by this is meant that it depends on by this, difference not extremely visible, are only meant this is certainly holds good true. But if we take the more common acceptation, of adaptive as the duration of life, period of flowering, adaptive to climate &c.— then, although this view does seem to cannot be considered as generally holding good in some cases, though it may apparently does in — some cases.

40

(27 Hybridism

to cross the many nearly related forms of Crocus: whereas he succeeded with the many extremely diversified distinct forms species, ranked as genera by some authors, of Narcissus (Hort. Journal vol 2. p 14-20) whereas some species conspicuously different have freely united (a) In the same natural family the species of one genus will unite cross very easily & yield hybrids usuallymore fertile than usual, as for instance (& many others might have been given Gaertner Bastarderzeugung p. 126) in the case of Dianthus, whereas another closely related genus with apparently equally close species gave no result viz, Silene yielded no hybrids in the experiments of Kolreuter & excepting interbred Silene Gartner,— Even within the limits of the same genus, certain species will not cross, whilst the others will with remarkable readiness; of this Gaertner gives (p. 147. Bastarderzeugung) a very curious instance in Nicotiana acuminata, which failed to unite with fertilise or be fertilised by eight other species, whereas the species of this genus have been more largely crossed than those of almost any others. Gaertner These facts certainly show that though very remote plants certainly will not cross, systematic affinity does not give the law key to the law regulating the capacity of sexual union. We shall see these facts proven by reciprocal crosses. Indeed so variable is the fertility fertilitysuccess of crosses of the same of the two same species crossed made under apparently similar circumstances, that that ((Gaertner indeed has remarked, the law must depend cons to a considerable extent on the constitution individual (p. 143) & p. 406) of each individual not, of on the species, but of the individual; by which means he accounts for the as he partly infers from fact of certain individual specimens (p. 164 Bastard) obstinately refusing to cross & from other facts: & he infers concludes (p. 143) that it is impossible without before repeated actual trials to predict which species will unite & which will not. So again the degree of sterility (p. 366) of Hybrids raised from seed out of the same capsule is very different, showing that much depends on the individual.—

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(a) as in the genera Rhododendron, Az first united, & soon we shall adduce other remarkably different species which have joined

p 164. Gaertner Bast. case of 2 Pentstemon so close as to be thought only vars. which will not cross.— (*) & at p. 174. 174 (Q) he gives whole list. In the same genus, as Kölreuter / has remarked with regard to the species of Digitalis. (Gært. p 175) species not the most nearly related species. this propinquity does not go with capacity for hybridising & G. gives strong example. (in Nov. Com. At. Sci. nat. Petrop. 1775. p. 447 quoted from Gaertner.)

p. 178 cases of unlike species which unite.

Herbert. (Amaryll. p. 343) gives the case of Crinum Capense, Zeglanicum æsculum, as being very similar in general appearance & yet producing extremely sterile hybrids, whereas, C. Capense & pedunculatum are as unlike perhaps as any 2 species of any Known genus, & have indeed been placed in different genera & yet they yield a fertile cross.—

Herbert in Hort. Journal asks why vol. 2. p. 10 asks how is it that in the g. Hippeastrum that all the natural species forms or varieties of Hippeastrum breed more readily by the pollen of any other, however complicated by cross-breed, than by its own; & that in the genus Habranthus, most closely allied to it, every attempt to cross the natural sort has as yet entirely failed.

Lindley on Apple &

(*) Herbert. (Hort Journ vol 1. p. 95.) in Pelargonium it is impossible to cross the race to which the horse-shoe scarlet belongs or that to which the tricolor belongs, with those which the florist has intermixed "with very little apparent structural difference, there seems to be a secret insuperable bar". (better says speaking of certain sections of the genus p. which has undergone so much crossing….

Gaertner (p. 194.) says there is even less relation in the fertility of the resultant hybrid to systematic affinity than in the hybrid first union.—

(Lindley Gooseberries & Peas & Apples)

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(28 Hybridism

has shown that often times Gaertner (Bastard p. 180, 183 strongly marked external differences in species such as in in the form of the flower, as size & shape of the fruit & seed in the shape structure of the of pistil, in in the size of the pollen-grains, shape of the Cotyledons leaves (p 275) leaves do not prevent the union. Again we have species characterised by the most remarkable diversity in general habitus, which will unite easily: thus Herbert has described (Amaryll. p. 364) a cross between a shrubby & herbaceous Calceolaria & a still more remarkable one between two species of Erythrina, (Hort. Journal. vol 2. p. 102) one of which bears produces its spikes of flowers directly from the root, & the other is almost arborescent & blossoms from the axils & ends of the leafy branches. But in the Cacteæ we have the most surprising unions, as between (Herbert, Amaryll. p. 345) (Gaertner Bastard. p 179) the prickly , angular Cereus speciosissimus, the whip-like C. flagelliformis, & the flat-unarmed phyllanthoides; & the first of these species has been crossed with the Melocaetus ottonis; & other similar crosses with species of Echinocactus, Echinopsis & & of allied genera have likewise, been effected.

Herbert, in Introduction part of his admirable treatise on this subject, has insisted expressed a strong opinion that the facility of crossing depends on — chiefly on similarity in constitutional characteristics peculiarities similarity: I presume that by constitutional characters, as opposed to systematic are meant such as in a specimen are extern not visible to the eye, such as perio adaptation to climate & soil period of existence duration of life, times of flowering &c &c.— This does seem to hold good in some cases; yet yet many

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(29 Hybridism

known facts, some observed by Herbert himself, seem opposed to the conclusion. Thus. the tender Rhododendron arboretum has been crossed (Amaryll. p. 360) with the hardy R. pentium & even with R. Dauricum which flourishes round Lake Baikal in the intense climate of Eastern Siberia. In the crosses between Rhododendrons & Azalea we see evergreen & deciduous bushes united; and Gaertner has shown (Bastard p. 143) that a difference in the time period of flowering, does not & & in the duration of life, viz in being annual or biennial & perennial does not prevent union. In the fertile cross hybrids obtained by Dr T. B. Salter (Phytologist) between Epilobium montanum & tetragonum, we see the blending of — plants living in, moist very damp & dry situations; other additional facts might be given.—

The remarkable class of facts first observed by Kölreuter, shows I think far even better than the above special cases, that, (Thus as has been remarked by Gaertner, (Bastard s. 176) that neither systematic affinity, or resemblance in general habit, or similarity in constitutional peculiarities will account for the variable capacity or unique for union in certain of between certain species to make together & for the the [illeg] of others & for the entire refusal of others species to produce hybrid offspring: I allude to the fact that there are many cases in which species A will breed can be fertilised by the pollen of B, but B cannot absolutely resists receives with great difficulty the action of the pollen on A*. Thus Kölreuter (Nova acta Pertol. 1793 p. 391 [illeg] 397) found the Mirabilis Jalappa when fertilised by M. longiflora, produced a good many plants hybrids, & these self-fertilised yielded even "numerum non adeo exiguum" but the reciprocal cross. ie. M. longiflora, fertilised by M. Jalapa

42v

G. finds that this unique capability of in reciprocal crosses holds g was in extremely general in all intermed & & lesser a lesser, degrees,: & steadily graduates away it may be observed even between extreme species [illeg] relation to each other, as in Matt am &. Del.., which some Botanists think are only varieties, ( ) It is also, an important fact that the hybrids raised fr reciprocal crosses themselves have not equal, sometimes sometimes very unequal fertility. These facts are the more strange*, as being almost universally generally* the hybrid plants from reciprocal crosses are quite so like as to be indistinguishable; (yet they cannot, though apparently alike, be really identical in their inmost nature, for besides the difference in their fertility, it is found, that there is sometimes a difference in the time required to reduce them to the p either parent form by successive crossing with either pure) parent Whether Under special Laws or when Mongrels & Hybrids are compared. ??

Now it seems impossible in these numerous cases to say that species A. will not cross absolutely refuses to be be fertilised or is cross be fertilised wi with great difficulty, with by the pollen of B. on account of any systematic or, as it comes same constitutional or other sim differences, while at the it is found that the very same species B. can easily be fertilised by the pollen of A. We are driven to look to some mere difference solely in the sexual relation of the two species; which Gaertner calls Wahlverwandtschaft or elective affinity, & which I have called sexual affinity; including under this term the relation of the pollen to the stigma, as well as to the ovule & stigma to pollen, as well as to the ovum of f & possibly perhaps even to the life of the embryo as long as nourished by in within the seed, of the pu as long as nourished by the parent formed by the pure mother.

(If in the reciprocal crosses: there had been only ocasional instances of an entire or almost entire refusal to cross on one side; we might have been attempted to explain the fact by some physical obstacle found in the pollen tube not being imbibed readily to ovule; in fact that the

*It might be asked in these cases, do not the ovules with their double nature, perish in one case before maturation, but in the other case live, the ovule of A fertilised by B,& the reciprocals, may at first be alike, but they are exposed to different conditions in the carpels of the two species. ؟ —Yet their is some difference in their reciprocal crosses for they are absorbed at different rates. (Gaertner Bastard. P. 459, 465) If there be any truth in this suggestion the importance of following reason is rather shaken. It is not pretended that hybrids themselves resulting from reciprocal crosses differ in fertility.

42a

more than 200 times, during 14 years never yielded and entirely failed: (Kolreuter gives other nearly as striking cases in the genera Lycium & Linum (Acta Acad. Petrop. 1778, p. 219; Nova Acta Petrop. 1783 p. 339).

This holds with trees

42av

there had been no true Known impregnation on one side; but this view does not seem to agree with the graduated degree of unequal infertility in reciprocal crosses. & still less with the unequal of fertility of the hybrids when actually produced from reciprocal crosses. It may possibly be that on average equal number of ovules are really fertilised in the reciprocal cross. but that all or a greater number or all perish when nourished in the seed of one parent, than in that of the other: this point does not seem to have been attended to by microscopical dissection. But then how are we to account for the unequal fertility of the hybrids themselves, when raised from the their reciprocal cross?

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Hybrids Similar cases have been given with ample details by Gaertner (Bastard s. 196) (a) & he has further shown what appears to me very important that this difference of fertility in what may be conveniently called "reciprocal crosses" is very general common in a lesser degree (s. 177) & graduating away may be observed even in very closely allied species, (s. 177) p. 197) as in Matthiola annua & glabra Datura stramonium & tatula &c, &c which some Botanists consider as only varieties. (Now it cannot hardly be said seems impossible that B will not be fertilised by A, on account of systematic or constitutional differences, when by only reversing the sexes, A will unite pretty freely with B: ( we see can only conclude with Gaertner that each form has is endowed with a peculiar elective (wahlrerwandtschaft) or sexual affinity; the same species having often a different affinity with towards another species relatively to the sexe employed in each in the attempt to the reciprocal crosses. them.

(P)This difference in fertility in accordance to hybrids from reciprocal crosses in all the more surprising, in as much as the hybrid offspring do not as shown by Kolreuter & (Gaertner ( s. 201) (p 223 p. 225) necessarily or usually usually* differ in structure or appearance as is so often the case with hybrid animal, for instance as in the well known case

43v

If only few cases of great difference ought hybrid to explain by some merely physiological difference of pollen, but [illeg] explain the gradation cases — & thus no light. see Bot of p. 29.

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p. 30 test (a)

I will give only one two, (p. 147, 199) (176 general results on this head) viz that of Nicotiana Langsdorfia, which will fertilise from other Kinds & so produce a few seed but cannot be fertilised by these four or indeed by four other additional Kinds of tobacco.Gaertner has Aquilegia vulgaris & Canadensis The common & Canadian columbines (p 195) bea naturally yield nearly the same number of seed,: but the former fertilised by A.quilegia canadensis gave as Maximum 151 seed, whereas A. canadensis fertilised by A. vulgaris yielded a maximum of only 29 seeds.— Fucus

* It is singular that the genus Digitalis was found both by Kölreuter & Gartner (p 225) to offer several marked exceptions to the likeness of the offspring from reciprocal crosses.—

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(31 Hybridism

of the mule & hinny; which differences perhaps might be attributed to the males & females of animals differing in structures in the animal Kingdom. & but rarely in the vegetable Kingdom [illeg] Yet I may remark, there is besides a fertility differ condition No

G. B

p 406 = when reciprocal crosses can easily be effected, Hybrid generally fertile & conversely p 200

If sterility had been ordained simply to prevent the confusion of specific forms, I think it might have been expected that there would have been a decided relation between the difficulty in effecting the first cross, & between any 2 species & of the fertility sterility of thir resultant hybrid offspring— To a considerable extent this certainly holds good; if two species plants can be very easily crossed more especially if they can be easily crossed reciprocally their hybrid are almost generally generally usually tolerably fertile (p. 406 Gaertner) & covering when the show; but there are some strong & curious exceptions (p. 407) to this rule. hybrids from the reciprocal cross though absolutely identical in appearanceresembling each other are each near have quite great fertility.— And The resultant hybrids,are [illeg] theates, differ in fertility even from reciprocal crosses As a general rule the hybrids themselves yield with their own pollen, & even with pollen of pure parent (p. 425 Gaertner) far less seed than the first cross between the two par pure parent species; but the by many some few hybrids (Gaertner p. 13) as in genera most many species of Datura & Dianthus yield more tho seed than their parents when first crossed. On the other hand there are many most striking cases of plants which can be united with facility, whose hybrid-offspring are excessively or even absolutely sterile: thus (Gaertner p 405 & p. 194) Nicotiana suaveolens fertilised by N. glutinosa yielded in maximum in a single fruit no less than 256 good seed, but the hybrid from the cross N. suaveolens tri-glutinosa was

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(32

Hybridism absolutely sterile: Gaertner & Kölreuter have observed nearly similar & striking cases in Dianthus: (a) so again the closely-alike species of Verbascum unite so readily that this but rarely takes place , without any artificial aid (Gaertner p. 591 p 410: & Kolreuter Dritte Fort. p 32, 42) yet most of the hybrids are excessively sterile, as has been remarked by Kölreuter 3d Fort. p. 44 & Gaertner Bastard. p. 580.. Hence this fertility of the first cross & of the resultant hybrids certainly in many cases often follows very different laws.— I will now give a few more of the best ascertained facts to show on what special & curious complex laws the fertility of species when these crossed & this hybrid affinity depends.— Further to show how special & curious the laws the laws regarding tt the fertility of hybrids are, & how they must depend on the most depend on the most singular relations & causes, on which we Know nothing, I will select a few only some of the best established cases from Gaertner & Kölreuter When a hybrid is fertilised by the pollen of either parent-species it always (p 425 Gaertner) yields as already stated more seed than when fertilised with own pollen; (& if both pollens are mixed together & applied to the stigma its own pollen (p. 426) produceshas no effect whatever;) the pollen even of a third & quite distinct species is sometimes (p. 427) produces with a hybrids more seed than due its own.— more effective than its own. The offspring of the a hybrid with fertilised by the pollen of either pure parent of course approaches the latter in character, & by repeated similar crossings s finally reduced, (varying in the number of generations according to the species used & even to the individuals used) is the successive generations of hybrids are reduced to the character of that pure parent the pollen of which has be used.

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(a) Hence within the limits of this latter same genus (Kölreuter zweit Fort. s. 108. Dritte. Fort. s. 72) we have species which unite easily but their produce hybrids are most exceedingly sterile, & other species which unite with the greatest difficulty, but the resultant produce hybrids are very fairly fruitful.—

During the reduction of a species hybrid to either parent-form which requires more or few generations, according to the species experimentised on & even according to the individuals which happen to have been selected the variabil fertility is extremely variably; but as in the successive generations the hybrid approaches assumes the character of either, pure parent species the fertility gradually (with a few exceptions) increases; but sometimes is severely compromised after even when the hybrid perfectly resembles to the eye one of its pure parents — species, a Hybrids reduced by the use of the pollen of the mother-species, acquires fertility fertility in the successive generations quicker, than the same hybrid does, does when reduced by the pollen of the father species [illeg]. (453). In all cases Hybrids of all kinds, all cases the male side suffers [illeg]; is the first to suffer; that is the fertility, on the male perfection of the pollen is sooner presents suffers sooner impaired compromised imperfection, & more slowly is latest is more slowly regained reestablished reperfected during reduction, than the is the capacity for fertilisation in of the ovule. to be fertilised

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P. 30

It is also a most important fact that the hybrid themselves resulting from these reciprocal unions often have themselves (p 407) very universally different degrees of fertility; being even in the case of Lavatera pseudolbio thuringiaca fertile

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(33 Hybridism

During the process of reduction the in the successive generations (Gaertner p. 419 to p. 455) the fertility of the hybrids is extremely variable, exc but , with occasional exception, increases as might be expected, as the hybrids approach in character to the pure species. But in some cases when the eye at last can distinguish no difference from the pure forms, the fertility still remains much impaired. Hybrids reduced by successive crossing with the pollen of the mother-species are (p 453) are more fertile than those reduced by the pollen of to the male-parent-species.—

In these No Hybrids also fertilised by their own pollen (p 420) in the first & succeeding generations offspring the fertility is excessively variable & often de lessened. In all cases the it is on the male side (p. 425 p 350, 355 & as observed by Kölreuter) that the fertility first suffers, & is last perfected repaired (p 435).

(All The ( Hybrids in to the first generation offspring from any the union of two species usually presents a fixed character all resemble each othera fixed character; but sometimes occasionally single seedlings are produced differing considerably from the others rest, & these are called by Gaertner, "exceptional types", & which ; very closely resemble closely either the father or the mother species; even though the & such normal hybrids of same parentage may have considerable fertility: these exceptional types & may & are generally almost always (p 244 my case) quite sterile.

Again Secondly, hybrids usually commonly are nearly intermediate in structure between their two pure parents; but there are some, species which produce regularly produce, what called by Gaertner calls, "decided types", which regularly approach either to take after one of the parents much more cloesely than the other. are not intermediate, but regular are in a a more & moreregular manner will approach muchmore closely resemble resembling much much

48v

wholly different, when a hybrid is fertilised by the pollen of a third pure species; the offspring which has only half in this case always closely resemble the pure Father, (though they having only half its blood) so closely a resemblance to appear merely as a slight variety of it: Kolreuter* was says he was almost as so much astonished at one of these such. cases, that he as if he had seen a lion born from a cat-- On the other hand, it is exactly reverse case, namely of a pure species fertilised by the pollen of a hybrid from two other species, (for instan L. fulg.) the hybrid does not take its form after its pure mother species, or after its hybrid father, but is excessively variable.* In many all cases in which 3 or 4 species are united the hybrids are very sterile variable & extremely sterile; but there is no sterility is not invariable, as Herbert case shows in genus Gladiolus & Crinum, even where 4 species are united. I am not aware that more than 4 species have ben compounded.

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(34 Hybridism

either even the father than or the mother — species, or the reverse: this is apparently caused by the prepotent power of one species over the other; These "decided types" ( p. 286) are, with some few few exceptions sterile. (a)

Again I hardly simple hybrids, fertile both whether single hybrids, Again, Hybrids in the successive generations, whether fertile by their own pollen, for or in one generation by the pollen of those even perhaps those which have been reduced one stage towards the parent or mother form, when fertilised by their own pollen likewise occasionally yield exceptional types (, like those from the first union of two pure species) which go back as it were & approach closely to either to the pure grandfather or more commonly the grandmother species-form; & in these exceptional retrograde forms, are the fertility (p 439, p 442) is lessened & sometimes entirely destroyed; of which this latter fact Kœlreuter gives several instances. Now in all these several these cases we have have the unexpected fact that close resemblance in hybrids to either pure parent-form if appearing exceptionally in a few of the hybrids, or if appearing in a very marked way "decided" may be all the less is connected with, it cannot be said causes or is caused by, lessened fertility; which a priori assuredly would never have been anticipated, ; & it stands in direct opposition to what usually & naturally takes place is the gradual & regular reduction of hybrids by the pollen successive applications of the pollen of the either parent species; This rare facts, shows also, how little fertility is related to mere external resemblance for this hybrid is the species that from character shares, fertility again ((a)) (B)

(There are many several cases where of two species which will unite with a third & distant species but will not unite with each other; thus Nicotiana rustica will unite with N. paniculata, as will also N. glutinosa; but N. rustica & glutinosa (Gaertner Bastardz p. 202) cannot be made to unite; so again it is with 3 species of Dianthus.)

B?

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(a) p 34

save This fact case no doubt stands in close relation with the fact rule, that when species can not be easily crossed reciprocally, then then produce often often are fertile sterile; for we it is found that those species which when crossed yield "decided types", cannot can very but seldom be crossed reciprocally (p. 221 p. 286) ie. thus if the hybrid offspring of A & B be nearly intermediate then A can be joined to fertilised by B . & B by A.; but if the offspring takes decidedly after either parent, then their reciprocal cross cannot be usually effected.

The species which yield the decided types can seldom be crossed reciprocally; & we have seen it is a gen rule, that species which cannot do not submit to reciprocal cross yield sterile sterile offspring.

51

(p 34 ((a)) (B) (So again Gaertner has shown (p. 289 that certain species in a genus when crossed with others have a predominating power in influencing the structure of the hybrid offspring; whereas other species have a prepotent power in capability of fertilising the other species, but that these two powers do not go together: & follow different laws.)

In the same genus, some species have, as already remarked, a prepotency over the other in transmitting there likeness to their hybrid offspring— other some species have a prepotency are prepotent in their capacity of fertilising the other other species, of the but these two powers do not go together.—

51v

In the same genus, A species may have much prepotency, that is when crossed with them it may have with species of the same genus a very strong power of transmitting its likeness to all its hybrid offspring. When crossed with other species of the same genus Another species may have a remarkable power of fertilising many the other species of the same genus; but these two powers by no means necessarily go together.)

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(35 Hybridism

If we put on one side those fer pow species (Gaertner p. 290 290 which have are endowed a peculiar prepotent power of when crossed with some other transmitting their likeness to their hybrid offspring, & which endowment as we have seen we have first seen I may remark does not gi at all accompany a prepetual power of fertilizing all other pure species or cisthe power of producing Hybrid offspring. these in all complicated mixtures the proportion structures of the hybrid depends on the simple proportion (of blood, as the breeders of animals would express it) in which the two species have entered into the composition of the seedling: are blended together: thus, the three following hybrid Pinks closely resemble each other (Gaertner p. 504)) for the proportion of each pure species is the same, though mingled in their different manner as far as the sexes are concerned. Yet they all closely resemble each other

I state these facts chiefly for the sake of showing how very singular the following case is which has been observed by Kölreuter & Gaertner (p 507) & Paris Journal., viz that when a hybrid is fertilised by a third distinct species, especially when the three species are very distinct, the offspring is which have only 1/2 the blood of the far yet always closely resembles the pure father, so closely (p. 516) as to appear sometimes as a mere variety: (B) on the other hand in the reverse case, when the a third pure third species is fertilised by the pollen of a hybrid from two other & distinct species (for instance Lobelia fulgens by fertilized hybrid) L. cardinali-syphilitica) the offspring are excessively variable (p 507) but does not take especially after the pure

53

(B) thus so again thus Kölreuter (1st. Fortset. s. 41 2) speaking of the hyprid raised by fertilising the hybrid from Nicotiana rustico-paniculata fertil by N. perennis with the pollen of N. perennis, says it is very like the latter or father, & that considering the great difference between N. rustica & perennis, he was says he was almost as much astonished at this hybrid, as if he had seen a cat had been born of the size of a lion.—

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(36 Hybridism

mother or after the hybrid father: in both case these hybrid plants, in which three species are united, are commonly excessively sterile. (B) So it is, & so perhaps it might have been so expected, in still more complicated crosses, as when four distinct species are blended together (G. 516), as for instance from the following hybrids from Lobelia cardinalis-fulgens, when fertilised by the hybrid L. syphilitico-splendens ; the offspring here are were excessively variable & quite sterile. (B)

(After Reciprocal crosses) *

(I will give only one other case from Gaertner p. 515 which I could not have credited, had it requires almost more than very great all one's confidence in Gaertners accuracy to credit: namely that if a hybrid, even a very total fertile hybrid be crossed with a reciprocal hybrid the offspring are quite sterile: thus if the hybrid Lobelia cardinali-syphilitica be fertilised by the pollen of the hybrid L. syphilitico-cardinalis the offspring are quite sterile: here we see there are only two pure species concerned, & the only difference between the two hybrids is that the sexes of their parents are have been reversed. Gaertner enumerates five cases, one of these the L very fertile Lychnis diurno-vespertina x L. vesp vespertino -diurna, which many some Botanists think are only varieties, & he appends one et cætera to the five, & concludes with "these hybrids we have found absolutely infertile." —)

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(B) These mixtures, ،however, of these or 4 species are not always necessarily sterile sterile, as we may see in Herberts compounded complex crosses in plants (Hort. Journal vol 2. p. 19, p. 88) of the genera Gladiolus, & Crinum (p 19). on the other hand