24 ESSENTIALS OF BOTANY 



is known as the peg. Study a good many seedlings and try 

 to find out what the lengthening of the hypocotyl, between 

 the peg and the bases of the cotyledons, does for the little 

 plant. Set a lot of squash seeds, hilum down, in moist 

 sand or sawdust and see whether the peg is more or less 

 developed than in seeds sprouted lying on their sides, and 

 whether the cotyledons in the case of the vertically planted 

 seeds usually come out of the ground in the same condi- 

 tion as do others. 



31. Disposition made of the Cotyledons. — The cotyledons 

 of the squash during the growth of the seedling increase 

 greatly in surface, acquire a green color and a generally 

 leaf-like appearance, and, in fact, do the work of ordinary 

 leaves. In such a case as this the appropriateness of the 

 name seed-leaf is evident enough, — one recognizes at sight 

 the fact that the cotyledons are actually the plant's first 

 leaves. In the bean the leaf-like nature of the cotyledons 

 is not so clear. They rise out of the ground like the squash 

 cotyledons, but then gradually shrivel away, though they 

 may first turn green and somewhat leaf-like for a time. 



The development of the plumule seems to depend some- 

 what on that of the cotyledons. The squash seed has coty- 

 ledons which are not too thick to become useful leaves, 

 and so the plant is in no special haste to get ready any 

 other leaves. The plumule, therefore, cannot readily be 

 found in the unsprouted seed, and is almost microscopic 

 in size at the time when the hypocotyl begins to show 

 outside of the seed-coats. 



32. Root, Stem, and Leaf. — By the time the seedling is 

 well out of the ground it usually possesses the three kinds 

 of vegetative organs, or parts essential to growth, of ordinary 

 flowering plants, i.e., the root, stem, and leaf, or, as they 



