362 



THE POPULAR SCIENCE MONTHLY. 



plants are not contented simply to leave their seeds on the surface of 

 the soil, but actually sow them in the ground. 



Thus in I'rlfoHum suhterraneuni, one of our rarer English clovers, 

 only a few of the florets become perfect flowers, the others form a 

 rigid, pointed head, which at first is turned upward, and, as their ends 

 are close together, constitute a sort of spike. At first, I say, the flower- 

 heads jjoint upward like those of other clovers, but, as soon as the 

 florets are fertilized, the flower-stalks bend over and grow downward, 

 forcing the flower-head into the ground, an operation much facilitated 

 by the peculiar construction and arrangement of the imperfect florets. 

 The florets are, as Darwin has shown, no mere passive instruments. 

 So soon as the flower-head is in the ground they begin, commencing 

 from the outside, to bend themselves toward the peduncle, the result 

 of which, of course, is to drag the flower-head farther and farther into 

 the ground. In most clovers each floret produces a little j^od. This 



Fig. 18. Vicia AMrnicAitrA. a a, ordinary pods ; b b, subterranean pods. 



would in the present species be useless, or even injurious ; many young 

 plants growing in one place would jostle and starve one another. 

 Hence we see another obvious advantage in the fact that only a few 

 florets perfect their seeds. 



