I20 COLIN CLOUT'S CALENDAR. 



and similar stunted creeping meadow plants, there is 

 not much material to spare upon the leaves, and so they 

 only develop one terminal leaflet with a sinc^lc pair of 

 lateral ones beneath it : in other words, they are shortened 

 into trefoils. The complementary leaflets on each stalk- 

 remain always undeveloped. In these vetches, a^c^ain, 

 and still more in the true peas, it is the terminal leaflets 

 that are wanting ; and in their place the end of the 

 common leaf-stalk lengthens out into twining tendrils, 

 which help the branches to creep over other plants, so as 

 to gain a decided advantage in the struggle for life over 

 the little procumbent clovers. 



Sometimes among the peas, however, circumstances 

 call for a different modification ; and then we get all 

 sorts of curious distortions or abortions, as the case may 

 demand. Thus the beautiful pink grass-pea, growing 

 among tall blades on borders of fields, requires foliage 

 like the grasses themselves, in order to compete with 

 them on terms of equality ; and it has achieved its end 

 by dwarfing the leaflets till they have disappeared al- 

 together, while at the same time the denuded leaf-stalk 

 has flattened out into a broad blade, exactly imitating 

 the grasses among which it lives. In its close relative 

 the yellow vetchling all the true leaves are reduced to a 

 long tendril ; but to make up for them the barbed stipules 

 or flaps, normally mere tags about a quarter of an inch 

 long, have grown out into a pair of expanded and heart- 

 shaped green leaves. Here we must suppose that from 

 generation to generation the original leaflets got less and 

 less work to do, and so gradually died away by mere 

 disuse ; while at the same time the leaf-stalk in the one 

 case and the stipules in the other grew larger and larger 



