THE COMMON BEAN 9 



and of softest texture where the hilum is situated. The rest of 

 the seed after the testa is removed, is of oval flattened shape 

 similar to the complete bean, and is divisible into two large 

 fleshy halves called cotyledons (Fig. 3, c), which, however, are not 

 completely separate from each other, but connected at the side 

 with a conical projecting body (Fig. 3, r), one end of which is 

 found to fit into a hollow cavity in the seed-coat exactly opposite 

 the micropyle ; the other end is bent and turned inwards between 

 the fleshy cotyledons. The extent and shape of this small curved 

 structure is most easily observed when one of the cotyledons is 

 removed completely ; it remains attached to the other as in Fig. 3. 



Ex. 2. — Soak some broad beans in water and keep them in a warm place 

 all night. Examine them next day and make drawings of the various parts 

 seen both before and after stripping off the testa. Observe the relative 

 position of the parts of the embryo in reference to each other and to the 

 seed-coat. 



Examine and compare the structure of the following seeds after soaking in 

 the same way : — Pea, scarlet runner beans, vetches, and red clover. 



The bean seed contains nothing more than what has already 

 been described ; the nature and relationship of its component parts 

 only become intelligible when the seed is placed in the ground 

 or maintained under certain conditions, and allowed to grow. 

 When growth commences the lower end of the small curved 

 structure (Fig. 3, r) elongates and breaks its way through the 

 coat of the seed at a point very close to the micropyle, but 

 not, as often erroneously stated, through the micropyle itself. 

 It soon assumes the form seen in Fig. 4, and is recognised as a 

 root of a young bean plant. The upper bent half, which lies 

 between the cotyledons, also pushes its way out of the same 

 opening in the seed-coat and develops into a stem, from the 

 tip of which leaves are gradually unfolded. It is thus seen 

 that the seed of a broad bean is a packet containing a bean 

 plant in a rudimentary condition. 



This plantlet is called an embryo, and the portion of it which 



