(1

[annotation not in Darwin's hand:] (A version of this appears in The different forms of flowers… 1877 pp. 228—

Final Results. Cowslip-Polyanthus 1863, /64/. 65/

[N.B. None of these notes need be looked at again besides these Final Results.) It wd be best to use terms legitimate & illegitimate

I raised from a short-st. plant by its own pollen 3 seedlings, one short-st. & 2 long-st. I also raised from a long-st. plant 3 long-st seedlings. These 6 Homomorphic seedlings plants were subjected to experiment during 3 years. The results must be given under 2 heads viz. one for the single short-st. plant & the other for the 5 long-st. plants; for the fertility of short- & long-st plants illegitimate seedlings differs when homo-fertil.

First for the short-st plant; 27 flowers were fert. during the 3 years with own pollen, but produced one pod alone, which contained the rather unusually large number of 23 seeds. Hence this plant is very sterile. Although many of the anthers were shrivelled & contained little or no pollen (N.B. insert discussion on contabescence near end of paper) yet the sterility of the plant was not solely due to the poverty of the pollen, for as we shall see, several other homomorphic plants yielded seed when fert. by it. Other experiments showed that the pollen was very poor. Nor was the female organ utterly sterile, for I obtained one pod with 26 seed by fertilizing 4 fl. heteromorphic by Homo pollen; hence the sterility of the plant is due to the weakened power of both male & female organs.

p. 2

Final Results

(Now for the 5 long-st. homomorph. seedlings

During the 3 years, no less than 160 fl. were fert. by own pollen, & these produced only 22 pods.

Now during the same years, 56 fl. of common long-st. cowslips of same age & grown in same situation, produced when Homo. fert 27 pods, that is very nearly half. Hence the homo-seedlings ought to have yielded 80 instead of 22 pods. These 22 pods contained on an average 15.1 seed; they ought to have contained an average of about 20 seed. On these same 5 long-st. homo. seedlings 24 fl. were fert. hetero-y by pollen from the first mentioned short-st. homo. seedling & produced only 9 pods which is a very small number for a Heteromorphic union, but they contained an average of 38 seed.

This is nearly as great an average as ordinary Cowslips yield; but then the average of 38 in one way is certainly false; for a large number of the seed was so poor & small that it certainly wd not have grown. In all cases it is very difficult to get the average of Primula seed; for when there are many, they are small, & when few, very large, & it becomes almost impossible to determine which seed ought to be ranked as good. Thus the average of 38 for the homo-long-st seedlings is largely due to 2 pods containing the extraordinary number of 75 & 76 seed & I do not believe that one of these wd have germinated.

p. 3

Final Results

Hence these 5 plants are apparently in some degree sterile even when hetero-fert. by pollen of homo. seedlings; when fert. hetero-morphy by good pollen of common Cowslip, some of the capsules yielded a full complement of seed. (a) The fertility of these Homo. plants varied greatly according to the season, & this might have been expected from what we know of hybrids. Thus in 1865 36 flowers of the long-st. hom. seedlings Homo. fertilised, though they produced only 12 pods, yet these contained an average of 21.2 seeds. which is quite as large an average as long-st common cowslip yield, when homo. fert. The different plants themselves also varied in a marked manner in fertility; thus one of the long-st. had 36 fl. fert. by own pollen & did not yield during one of the 3 years a single pod. Several of its anthers were brown & shrivelled, but some of the pollen seemed to be good; nor was the female organ quite impotent for I obtained one pod with good seed by a hetero-union. Another long-st. plant had 44 fl. fert. & produced only one pod: on the other hand a 3rd plant had 42 fl. fert. similarly with own pollen & produced no less than 11 pods. There is no great difference in sterility between the one short-st. & 5 long-st. homo. seedlings.

[3v]

(a) Yet taking whole 20 thus fert only 10 pods were produced, (which is a very small proportion for a Heteromorphic union, & & these contained an average of only 30.5 seed per pod.

p. 4

Final Results

The sterility of both forms is certainly great, tested in various manners herein indicated, but is chiefly shewn in all cases by the small proportion of flowers which when fert. produce pods; for sometimes when they do produce pods, these contain an almost full average of seed. The sterility of these 6 plants was shewn in another way, like that in the case of of many hybrids for on March 22nd I fert. many common Cowslip long- & short-sty flowers & on Ap. 8. these, from being fert., were all thoroughly withered; whereas many fl. on the homo. seedlings had been fert. no less than 15 days previously & they still remained in full flower for several days after the common C. They might be called everlasting fl. for they remained in full bloom for above a month after being fert.