ON THE MODES OF DISTRIBUTION OF PLANTS. 367 



lichens, and ferns. The spores of fungi are so minute as to require a 

 microscope to see them, and so numerous that Fries says he counted 

 in a single specimen of Meticularia maxima no less than 10,000,000.* 

 What wonder, then, that with seeds so minute and so numerous these 

 plants should be almost universally distributed ? Out of 200 lichens, 

 for instance, brought home to England by the Antarctic Expedition 

 under Sir James Ross, almost every one has been ascertained to be 

 also an inhabitant of the northern hemisphere, and most of them of 

 Europe. It is easy enough to imagine the wind capable of transport- 

 ing minute spores to immense distances over land and ocean. Many 

 plants not possessing small seeds are carried off bodily by the wind to 

 distant localities. Of these there is the " leap-in-the-field," or the 

 " wind-witch," inhabiting the steppes of southern Russia. " A poor 

 thistle-plant," says Schleiden, " it divides its strength in the formation 

 of numerous dry slender shoots, which spread out on all sides, and are 

 entangled with one another. . . . The domes which it forms upon the 

 turf are often three feet high and sometimes ten to fifteen in cir- 

 cumference, arched over with naked, delicate, thin branches. In the 

 autumn the stem of the plant rots off, and the globe of branches dries 

 up into a ball light as a feather, which is then driven through the air 

 by the autumnal winds over the steppe. Numbers of such balls often 

 fly at once over the plain with such rapidity that no horseman can 

 catch them ; now hopping with short, quick springs along the ground, 

 now whirling in great circles round each other, rolling onward in a 

 spirit-like dance over the turf, now caught by an eddy, rising suddenly 

 a hundred feet in the air ; often one ' wind- witch ' hooks on to an- 

 other, twenty more join company, and the whole gigantic yet airy 

 mass rolls away before the piping east wind." 



Still another plant, the so-called "rose of Jericho," but really one 

 of the Gruciferoi, has a similar method of dissemination. Professor 

 Lindley says of it : " At the end of its life, and in consequence of 

 drought, its texture becomes almost woody, its branches curve up into 

 a sort of ball, the valves of its pods are closed, and the plant holds to 

 the soil by nothing but a root without fibers. In this state the wind, 

 always so powerful on plains of sand, tears up the dry ball and rolls it 

 upon the desert. If in the course of its violent transmission the ball 

 is thrown upon a pool of water, the humidity is promptly absorbed by 

 the woody tissue, the branches unfold, and the seed-vessels open ; the 

 seeds, which, if they had been dropped upon the dry sand, would never 

 have germinated, sow themselves naturally in the moist soil where they 

 are sure to be developed, and the young plants will be certain of nour- 

 ishment. Specimens of this curious production are sometimes brought 

 from Palestine, and, although they may be many years old, will, if 

 placed in water, start, as it were, from their slumbers, and assume all 

 the appearance of plants suddenly raised from the dead." The Sela- 

 * Quoted from Lindley by Lyell, " Principles of Geology," vol. ii., p. 390. 



