78 THE POPULAR SCIENCE MONTHLY. 



by human agency ; while our two more truly wild species are meadow 

 and pasture weeds, and are therefore amply protected by prickles 

 against herbivorous animals. Again, bird's-foot trefoil, whose pretty 

 yellow flowers form such ornaments to our sunny banks in summer, 

 has a long, hard, dry pod, too stringy to be edible, and filled with pith 

 between the beans ; while lady's-fingers, a somewhat similar type, has 

 an inflated hairy calyx completely inclosing the short pod in its pro- 

 tective and inedible capsule. Strangest of all, however, is the small, 

 matted bird's-foot, whose pod never opens to shed the seeds, but di- 

 vides between them into little joints or " articles," each inclosing a 

 single bean, and so cheating the expectant birds of their promised 

 food. These examples, which might be multiplied ihdefinitely, will 

 sufiiciently serve to show the importance of protection for the seeds as 

 a basis of differentiation among the papilionaceous flowers. 



With the restricted tribe of clovers the need for such protection 

 has almost alone produced all the species into which the genus has 

 long since split up. Originally, of course, we must suppose that there 

 existed one united type of ancestral clover, differing from the other 

 papilionaceous plants in the points which now distinguish the whole 

 clover genus, but possessing none of the special distinctive marks 

 which specifically divide one kind of clover from another. This 

 hypothetical ancestor had probably rather large, purplish flowers, 

 collected in compact heads on a common foot-stalk, with the five 

 petals separate, and with a small three or four-seeded pod completely 

 inclosed within the faded brown petals. From some such form the 

 existing clovers have sprung by differentiations almost entirely 

 affecting the pods and seeds, though they have also varied a little in 

 color, according to the individual tastes of their particular insect 

 visitors, as well as in the degree of union effected between their 

 petals. Without going beyond the limits of our own native clovers, 

 we will look first at those types in which the arrangement of the pod 

 is simplest, and then pass on gradually to those in which it is more 

 and more complex, till we arrive at last at that most marvelous Eng- 

 lish species which actually buries its own pods entire in the ground 

 by a wonderful scries of apparently purposive movements and gyra- 

 tions. 



Our common English purple clover (for convenience' sake I 

 adopt throughout Mr. Bentham's vernacular names) may be taken as 

 a good specimen of the simpler and less-protected kinds. The mere 

 fact that it is grown extensively for fodder shows that it has no deter- 

 rent prickles or bristles to ward off the attacks of herbivorous ani- 

 mals ; and indeed, throughout the clover group, it may be noted that 

 birds and insects, rather than large mammals, seem to be the enemies 

 especially guarded against by the majority of plants. Purple clover 

 is a perennial, with long, hairy stems, the hairs serving to prevent ants 

 from creeping up to the blossoms and uselessly rifling the honey 



