SOME PLANT BIOGKAPHIES. 207 



of leaves is exposed in summer to the sun and 

 air at the outer circumference of the dome- 

 shaped mass ; and in this way every leaf gets 

 its fair share of light and carbon, and interferes 

 as little as possible with the work of its neigh- 

 bours. Old beeches will grow to more than 

 100 feet in height, and live for probably three or 

 four centuries. At last, however, their proto- 

 plasm grows old and seems to get enfeebled ; 

 the trunk decays, and the entire tree falls first 

 into dotage, then dies by slow degrees of pure 

 senility. 



The common vetch is another familiar plant 

 whose life -history introduces to us some totally 

 different yet interesting features. It belongs to 

 the wide-spread family of the peaflowers, to 

 which I have already more than once alluded, 

 and it takes its origin from a comparatively large 

 and rich round seed, not unlike a pea, whose 

 cotyledons are well stored with supplies of starch 

 and other food- stuffs. It sends up at first a 

 short spreading stem, which twines or trails 

 over surrounding plants, developing as it goes 

 very curious leaves of a compound character. 

 Each leaf consists of five or six pairs of leaflets, 

 placed opposite one another on the common 

 stalk in the feather- veined fashion. But the 

 four or five leaflets at the end of each leaf- 

 stalk do not develop any flat blade at all, and 

 are quite unleaflike in appearance : they are 

 transformed, indeed, into long thin tendrils, 

 which catch hold of neighbouring branches or 

 stems of grasses, twine spirally round them, and 

 so enable the vetch to climb up bodily in spite 



