THE BROAD BEAN PLANT. 15 



leaflets (note their folded appearance at first) and is pro- 

 longed into a rudimentary tendril. After several leaves like 

 this we get leaves of the mature type, in which the stalk 

 is lengthened below the terminal pair of leaflets, and carries 

 two, three, or four additional leaflets. Have these early leaves, 

 like the later ones, buds in their axils? In the first two 

 leaves that appear on the young stem the three lobes evidently 

 represent the two stipules and the rudimentary tendril. 



36. Seedling compared with Seed. Carefully pull up 

 a seedling without injuring the root, and compare the latter 

 with the root of the mature plant. Trace the young root 

 upwards and the young shoot downwards, and notice the torn 

 seed-coat and the cotyledons. In the axil of each cotyledon 

 there is usually a bud. The cotyledons are therefore leaves, 

 though differing from ordinary leaves (foliage-leaves) in many 

 respects. They are often called the " seed-leaves." 



The young plant, or seedling, has evidently grown from the 

 whole of the seed-contents (i.e. everything inside the seed-coat) , 

 for we have seen that even the cotyledons are leaves, having 

 buds in their axils. The cotyledons are the first leaves of the 

 young plant, which is called the embryo while still inside the 

 seed. The embryo consists of an axis which bears the two 

 cotyledons at about the middle, and which ends in a root 1 

 (covered by a root-cap) at one extremity and a bud 2 (bearing 

 young foliage-leaves) at the other. 



37. Seedling compared with Mature Plant. We 



have noted the simple form of the earliest leaves as com- 

 pared with the older ones. The cotyledons are opposite each 

 other and are attached to the same point on the axis, but the 

 early foliage-leaves show the same arrangement (alternate, in 

 two opposite rows) as in the mature plant. The root of the 

 seedling shows the same general appearance and structure as 

 that of the mature plant, into which it grows, later on forming 

 the characteristic nodules. 



1 The root of the embryo is termed the radicle. 



2 The shoot-bud of the embryo is called the plumule. 



