76 THE POPULAR SCIENCE MONTHLY. 



among the surrounding grasses in sucli a way as to get freely at the 

 sun and air, which are necessary for the nutrition of the plant. But 

 the chief peculiarity of the clovers is the arrangement of their flowers 

 in dense heads. Instead of the blossoms growing separately or in 

 pairs, as with most peas and vetches, or in long, loose bunches, as with 

 laburnum and sainfoin, the flowers of the clovers, much reduced in 

 size, are crowded into compact little bundles, for the most part at 

 the end of a long stalk. What we ordinarily call the flower of a pur- 

 ple clover is, in fact, such a head of clustered flowers. This dense 

 clustering of the flowers makes them, though individually small, very 

 conspicuous in the mass to bees and other insects, and so largely in- 

 creases their chance of cross-fertilization. For the same purpose they 

 usually secrete abundant honey, and they possess in many cases the 

 familiar fragrant clover perfume. Moreover, in most though not in 

 all species the bases of the five petals have grown together into a 

 narrow tube, inclosing the honey ; and in the common purple clover 

 this tube is so deep that no British insect except the humble-bee has 

 a proboscis long enough to reach the nectaries. Such peculiarities 

 are quite sufticient to give the clovers an immense advantage in the 

 struggle for existence ; and it is not surprising that they should have 

 become exceptionally numerous in species and individuals, even among 

 the richly endowed and dominant papilionaceous family. 



Every race, however, has its weak as well as its strong points ; 

 and the weak point of the highly successful clovers lies in the unpro- 

 tected position of their seeds and pods. Hence, in accordance with 

 the general principles above laid down, it is in these particulars that 

 we might expect to find the various species differ most from one 

 another, since this is just the part on which natural selection of favor- 

 able varieties is most likely to be exerted. As in the papilionaceous 

 family as a whole, the flower is the organ which remains almost identi- 

 cal throughout, because it is the organ which gives the family its true 

 importance ; so in the restricted clover group the trefoil leaflets and 

 the clustered heads of flowers remain almost identical throughout, and 

 for the like reason. But in any classification of the various species of 

 clover, it will be seen by anybody who looks into the matter that all 

 the distinctive characters are drawn from differences in the pod and 

 calyx after flowering, because this is the weak point of the genus, and 

 the one in which alone diversities of habit have been likely to arise 

 and to be perpetuated by survival of the fittest. The other organs 

 have long since reached their equilibrium ; these organs alone remain 

 in need of further equilibration. 



And why is the pod a weak point ? For this reason. The seeds 

 of clover, though small, are very richly stored with starches and other 

 food-stuffs for the growth of the young plant. Such richness is, of 

 course, in itself an advantage to the race, because it allows the seed- 

 lings to start well equipped on the path of life, with some accumulated 



