ENTOMOLOGIST AND BOTANIST. 



277 



§0ta;iTud gtparlmntt. 



;eorge vasey, ed 



ORIGIN OF PRAIRIE VEGETATION. 



Various theories have been propoumled to ac- 

 count for the existence of the Western prairies. 

 By some they have been attributed to tlie an- 

 nual burning of the grass by Indians; by some 

 to the extreme fineness of the prairie soil, and 

 by others to humidity and sourness of the soil, 

 &c. One of the most recent theories on this 

 subject is tliat of Prof. Winchell, whose views 

 are developed in an article in the American 

 Journal of Science and Art, Nov., 186-1; and 

 again presented, somewhat amplified, iu his 

 recent work, entitled " Sketches of Creation." 



These views are peculiar, and as the points 

 involved come somewhat within the field of onr 

 department, we propose to discuss the principal 

 propositions which Prof. Winchell advances. 



The first proposition is that " the prairies are 

 of lacustrine origin;" from which statement 

 we see no reason to dissent, especially as it ap- 

 pears to be the view entertained by geologists 

 generally. 



The second proposition is that " lacustrine 

 sediments contain no living germs." This is a 

 somewhat sweeping assertion. Let us consider 

 it a moment. It is well known that lake borders 

 are the chosen locations of very extensive vege- 

 tation. Wherever there is a shallow margin, 

 some species of plants find a favorite home. 

 Extensive patches of gigantic bulrushes [Scirpus 

 validns, Vahl) grow in water six or eight feet 

 deep, and stretch up several feet above the 

 water, spreading out in many cases a mile 

 inward. Great beds of Water-lilies {Nymphea 

 and Nuphar), and allied plants, spread their 

 broad leaves and expand their beautiful flowers 

 on the bosom of the tranquil lake. Numerous 

 kinds of Pond weeds, (Potomayeton) Eel-grass, 

 Water-weed (Anacharis), &c., form large sub- 

 terranean meadows, through which the canoe 

 of the Indian finds it difficult to penetrate. Here, 

 too, on the lake margin, the Indian finds his 

 spontaneous fields of wild rice (Zizania aquati- 

 ca, L.) Sagittarias, Sparganiums, and water 

 weeds of various kinds, inhabit the shallow 

 borders in abundance. Every year these plants 

 mature an immense crop of seeds, which, except- 

 ing such as are devoured by birds and other 

 animals, fall into the water, and generally by 

 their own gravity sink to the bottom, where 

 they find, in the soft mud, a suitable place for 



their future germination. We know not how 

 many of these seeds ai-e carried out into the 

 deep portions of the lake, beyond the reach of 

 those conditions necessary to their growth. 

 Evidently Nature intended these seeds to ger- 

 minate at the bottom of the shallow lake margin, 

 and the only means they have for reaching that 

 locality is their specific gravity. As in the case 

 of land plants, Nature provides a surplus of 

 seeds in order to insure a continuance of the 

 species in spite of all ordinary contingencies. 



We then present a counter-proposition to that 

 of Professor W., viz: that lacustrine sediments 

 abound with living germs. We do not, how- 

 ever, desire to make use of this proposition in 

 accounting for the vegetation of the prairies, 

 lor whenever our lake bottom is drained it fur- 

 nishes no longer the conditions necessary for 

 the germination and growth of these plants, aiul 

 the seeds would probably soon perish. But, 

 whenever the soil is thus drained, the aquatic 

 plants are speedily succeeded by others adapted 

 to the new circumstances, the germs or seeds of 

 which are introduced from outside. 



The third proposition of Prof. Winchell is as 

 follows: "Diluvial deposits, on the contrary, 

 are found everywhere replete with living germs." 

 By diluvial deposits we understand those collec- 

 tions of sand, gravel, clay, &c., which have been 

 carried down by floods, or heaped together by 

 violent action of the sea, or have been plowed 

 up before the onward nnxrch of glaciers. Such 

 deposits, Professor W. says are replete with 

 living germs. In other words, they are filled 

 with living seeds. This proposition is illus- 

 trated by some examples which seem pertinent, 

 and by some which do not. 



It is stated that forests cleared of their timber 

 are almost " always followed by the appearance 

 of certain unwonted plants known as fire-weeds, 

 and it can hardly be doubted that the germs 

 existed in the soil ready to germinate whenever 

 free sunlight, warmth and atmospheric air 

 should be permitted to rouse their vital energy." 

 The term fire-weed is commonly rather loosely 

 applied to several different plants, chiefly to 

 those botanically known as Erechtites hieraci- 

 folia and Erigei'on canndense. These are al- 

 most as common as thistles, and like them have 

 light feathery seeds, adapted to be carried to 

 great distances by winds. Now, it appears to 

 us to be a good rule to explain any phenomenon 

 by the simplest and most obvious causes ; and 

 to our mind it seems much more natural to 

 account for the appearance of the fire-weeds by 

 the introduction of the seeds by means of winds, 

 than to do so by supposing that the seeds of 



