18 BEAN. [CH. II 



from inside the seed-coats; as it does so the testa is 

 seen to give way in the form of a triangular flap, which is 

 shown in fig. 12. But before this stage of germination is 

 examined the structure of the bean-seed must be further 

 described. On splitting it open, the young plant inside is 

 seen. By far the larger part of the plant is made up of 

 two thick fleshy lobes, whose inner faces are flat and lie 

 against one another, and whose outer faces are slightly 

 rounded and impress their form on the seed. These are 

 the two cotyledons or first leaves of the young bean-plant. 

 Similar cotyledons are familiar to most people in split 

 peas, which consist of little hemispheres, each being a 

 cotyledon ; in the almond too, the oval cotyledons, flat on 

 one side rounded on the other, are familiar enough. The 

 cotyledons of the bean are attached, by stalks at their 

 bases, to a minute stem, one opposite the other. This 

 axis is what will develope into the stem of the bean 

 at one end, and into the root at the other. The end 

 which grows into a stem and which lies between the 

 cotyledons is the plumule, the other end which terminates 

 in the primary root is known as the radicle. We see in 

 the bean our first example of the general plan of archi- 

 tecture common to a great number of the flowering plants. 

 The plant consists of a short axis or stem-like part, from 

 which spring side growths, in this case primary leaves or 

 cotyledons. We have here, too, an instance of the division 

 of the plant body into two parts destined to have dif- 

 ferent functions and corresponding!}' different structures 

 namely a roo-half, and a stem or shoot-halt It is an 

 example of a general characteristic of plants that very 



