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ON THE INFLUENCE O F THE WIND ON THE DISTRIBUTION O F SEEDS IN MOUNTAIN REGIONS.
et oí a paper by A Kemer. of Innsbrtclc. « the JemntaJ ,f Ou Gtrmmn Ai firn Ch
AlfintClmM ~ hot aftemoon in .the ^

----------- .n the shelter of a mountain ridge,

so that a ray of bright snnshine is intercepted by a

project ing pinnacle of rock, we see, in the immediate

vicinity of this piece of rock, innumerable shining c

spangles dart apwards with the quickness of an arrow

through the snnshine. These spangles prove, on

examination. to be minate fruiti and seeds of pianta,

provided with tufts or tails of hair, carried upwards by
invisible, and leen only under circumstances ti
Chamber. With «he ceaatkm of »he ascending current of air at (onset, and the moistening of the air by dew, cloud, or rain, a large proportion of these seeds falls to the j^round, and strews the summits, ridges, and hollows

In order to ascertain what kinds^of plants are thus
i by the ageney of the w i by the moraines, where it is impossible to suppose ihat seeds can be deposited by any other means than the one we are considerine ; and the flora of the moraines must be a catalogne of plants whose seeds are distributed by the action of the wind A list of fire of these floras, from as many différent moraines, consistine of Iimestone, schisi, and gneiss, included IH species, the following orden being the inoat largely represented : —Composita, aj per cent ; Caryophyllese. io per cent. ; Gramineac, 8 per cent. ; Mosse«, Saxifrage*, and Sn Salica cete. 6 per cent ; Crucitene, « per cent. ; Ferri« and Rosacea?. 4 per cent. ; Scrophulariaceie. 3 per ?S>

cent. Of the smaller familles, the genera Valeriana, Epilobium, and Juncos occurred the most frequently. The invartigation of these lìJ--'*v - ---
those plants which belong to the gTaring pi the lower élévations ; and stili less common species belonging to the meadow or wood flora of the lowlands, as Caumagrostis montana. Senecio nemorensis, Epilobium angustifolium, and Aspidium Filix-mas,' which
It does not however follow, because only this limited number of species is found to grow and to flourish, more or less, on the moraines, that therefore seeds of other kinds are not brought by the wind. which are nnable eren to gemínate in such unfavou rabie circumstances. In order to determine this point M. Kerner made a carefal examination of the organic substances foond on the icy surface ofthe glacier itself. which were in places very numerous and belonged to both the animal aad vegetable kingdoms. The animals found were entirely dead or benumbed inseets belonging to the orden Lepkloptera, Ilymenoptera, Coleóptera, and Díptera, and consisting of 43 species, a considerable portion of which are found only in the highest moun-tain regions in the immediate vicinity of the gUciers, r.'g.. Sargus infuscatus, Ptiolina crassicornis, Erebia Cassiope and Manto, Zygsena exulans, Setina ramosa, and Argynnis Pales; more than half the species of very wide distribution, extending from the mountain valleys and neighbouring plains to the edge of the glaciers, very fcw being found nominally only in the mountain valleys. as Hesperia sylvanus, Agrotis Prónuba, Leuco-phasia Sinapis, and Aphis pícete ; and one only, the common honey-bee, being peculiar to coltivated dis-triets. None of the inseets found belong to extia-
1 ' le species, none of the kinds peculiar to the w
the glaciers haré either strayed volontarily, or been driren by the wind from districts immediately adjacent to the gúáer.

The task of determining the seeds found on the surface of the glacier was much more diflicolt. The seeds of manr alpine plants have hardly been de-scribed ; and in other instances it is difficult to dis-
e belonging to severa! différent Tnus. This was especi Jly the
ra and Sal«. Thirty-sii species, however, were determined with tolerable certainty, the majority of which were identical with the speces previoosly recorded as inhabitants of the moraines. Here again the same resnlts are esta-b'ished ; not a single seed is found on the glacier, as
Ucts seems inevitable, that the cooveyance of seeds, even when provided "with apparatus cakulated for floating in the air, by horiiontal cunents. takes place only within vety circumscribed limits : and that the prevalent opinion that they may be thus carried for rerv great distances is not sopported bv fac+s.

The higber mountain flora mav be divided. foc the corpose of this investigation, into two sections. The first cocsists of plants whose frait or seed is provided with some kind of appendage to facilitate its transport by the wind ; thev have a verv short span of Ufe. are coastantly changing their habitat, can exi*t on a surface of ground contàining scarcelv a trace of humus, and spring up with the createsi teadíness on the ledges or in the arrices of the bare« rocks ; of this kind constats by br the Unger portion of the m-vaine flora. The second kind is much le» migratorr. requìres a better seti and a Urger proportion of humos, has a longer sran of tifo, and ita fn.it and «ed are unpro-rided with anv apparatos for flight : the seeds. therefore. drop dose to the parent plant or can onlr be carried a short distance when extretnelv minute. TV large* and heariesî seed of this description foond o« the glaciers or moraines was that of SibbaMia ito-combats, measring I m ra. in dia meter. and wcìghing

a length of <vS—1 m m., a breadth of o.l^a.3 m.m., an1 weighs oabvao6m.gr.

^ M. Kerner thus snms up the resolts of his obserra-

1. Onlr dast-like substances. soeh as rollen, spores, diatom-scales, Ac. can be distriboted bv corrents of

air over wide stretches oí land and 5« ' -------- "

flights. and thas be bro^r ¡»io tb»

3- Fruir» and seeds e provided with a web-like floating apparat« that d». tends itself in dry air in the fora of a parachute, are carried upwards bv the ascending carrent of air which arises on sunnv davs in alpine regioas oa the cessa-tk» of the horiiontal wind : bat after sanset ther sink again to the ground at a small distance in a horiiootal zJÈ^IÈMmà Ae Obiect attaiaed by Ais floating

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other lunds are not brought by the wind. which are nnable even to germinate in such unfavourable circum-stances. In order to determine this point M. Kemer made a careful examination of the organic substance» found on the icy surface of the glacier itself, which were in places very numerous, and belonged to both the animal and vegetable kingdoms. The animais found were entirely dead or benùmbed insects belonging to the orders Lepidoptera, Ilymenoptera, Coleoptera, and Diptera, and consisting of 43 species, a considerable portion of which are found only in the highest mountain régions in the immediate vicinity of the glaciers, e.1 g., Sargus infuscatus, Ptiolina crassicornis, Erébia Cassiope and Manto, Zygaena exulans, Setina ramosa, and Argynnis Pales ; more than half the species of very wide distribution, extending from the mountain valleys and neighbouring plains to the edge of the glaciers, very few being found nominally only in the mountain valleys, as Hesperia sylvanus, Agrotis Pronuba, Leuco-phasia Sinapis, and Aphis picene ; and one only, the common honey-bee, being peculiar to cultivated districts. None of the insects found belong to extra» alpine species, none of the kinds peculiar to the warm valleys of the southern Alps are represented ; and the inference is unavoidable, that ali the animais found on the glaciers have either strayed voluntarily, or been driven by the wind from districts immediately adjacent to the glacier.

The task of determining the seeds found 011 the surface of the glacier was much more difficult. The seeds of many alpine plants have hardly been de-scribed ; and in other instances it is difficult to dis-tinguish between those belonging to several différent species of the same genus. This was especially the case with the genera Hieracium and Salix. Thirty-six species, however, were determined with tolerable certainty, the majority of which were identical with the species previously recorded as inhabitants of the moraines. H ere again the same resulte are esta-blished ; not a single seed is found on the glacier, as not a single plant on the moraine, which does not belong to a species inhabiting the immediately adjacent mountain slopes or valleys. The conclusion from these facts seems inevitable, that the conveyance of seeds, even when provided 'with apparatus calculated for floating in the air, by horizontal cúrrente, takes place only within very circumscribed limite ; and that the prevalent opinion that they may be thus carri ed for very great distances is not support ed by facts.

The higher mountain flora may be divided, for the purpose of this investigation, into two sections. The first consiste of plante whose fruit or seed is provided with some kind of appendage to facilitate its transport by the wind ; they have a very short span of life, are constantly changing their habitat, can exist on a surface of ground containing scarcely a trace of humus, and spring up with the greatest readiness on the ledges or in the crevices of the barest rocks ; of this kind consiste by far the larger portion of the moraine flora. The second kind is much less migratory, requires a better soil and a larger proportion of humus, has a longer span of life, and its fruit and seed are unpro-vided with any apparatus for flight ; the seeds, there-fore, drop close to the parent plant, or can only be carried a short distance when extremely minute. The largest and heaviest seed of this description found on the glaciers or moraines was that of Sibbaldia pro-cumbens, measuring 1 m.m. in diameter, and weighing 0.4 m.gr. The seed of Rhododendron ferrugineum has a length of 0.8—1 m.m., a breadth of 0.2—0.3 m.m., and weighs 0nly0.06m.gr.

M. Kerner thus sums up the resuite of his observations :—

1. Only dust-like substances, such as pollen, spores, diatom-scales, &c., can be distributed by cúrrente of air over wide stretches of land and sea in uninterrupted flights, and thus be brought into the alpine régions.

2. Fruits and seeds of flowering plants which are provided with a web-like floating apparatus that distends itself in dry air in the form of a parachute, are carried upwards by the ascending current of air which arises on sunny days in alpine régions on the cessation of the horizontat wind ; but after sunset they sink again to the ground at a small distance in a horizontal direction; and the object attained by this floating apparatus is not so much the adaptation of the seeds for long joumeys, as to enable them to settle on the projections and in the crevices of steep precipices and rocks, and to clothe with végétation these rock-walls which are not easily accessible by other seeds.

3. The presence of membranous margins and wings fcvours the transport of fruits and seeds by horizontal cúrrente of air ; the horizontal distance, however, over which these seeds are carried scarcely ever extçnds further than from one side of a valley to the other side, and the distribution of the fruits and seeds of flowering plante, in so far as this is caused by cúrrente of air, can only proceed gradually and step by step.

4. Fruits and seeds which are deficient in any kind of appendages which facilitate flight are scarcely influenced by cúrrente of air ; it is only when these •eeds are of very minute size and extremely small weight fhat they can be driven short distances by horizontal winds.

These resulte, insignifiant as they may seem, are of great importance in the solution of a whole series of questions relating to the geography and history of plante, which may here be briefly indicated.

If the seeds of flowering plante can only spread themselves step by step, an unbroken chain of habitats must have at one time existed between the outposts which each plant occupies on the extreme limit of ite area of distribution and the centre of this area. If the area of distribution is Interrupted for a considerable space, and if there 1s no possibillty of the carriage of fruits or seeds by some other agent of distribution, such as designed or accidentai transportation by raen, animais, or water -the interruption of the area of distribution, or Its splitting Into two, three, or raore sections separated from one another, can only have arisen in the course df time ¡ for the supposition that the seeds of flowering plants may be carried by eurrents of air from one mountain range to another, from one island to another, fs inadmissible, from the considérations advanced above. We find, however, in the Alps, in llmlted spots favoured by local conditions, group» of plants which otherwise have no wlde distribution, and only crop up again in the far south, and whose transportation by man, animais, or water can be negatived with certainty. These can only be considered as abandoned outposts of an earlier area of distribution connected by an uninterrupted series of habitats. The circumstance, however, that these colonies of southern plante occur on several points of the eastern Alps, forces us to the conclusion that since the Iast glacial pertod, a warmer climate must have relgned In the région of the eastem Alps, under favour of which these southerly plants were propagated far more widely in an unbroken chaln of habitats ; but that later, in conséquence of the change of the cllmatal conditions, these species retreated to more southerly réglons, and have only remained In northerly latitudes in isolated localities greatly favoured by the climat».