16 BEAN. [CH. II 



tiously removed and a lighted taper lowered into it is 

 found to be extinguished by the accumulated C0 2 . 



The point to which I wish to call attention is that 

 given water, free oxygen and a sufficient degree of 

 warmth, the growth of the young plant in the seed will 

 begin although no carbon, nitrogen, phosphorus, sulphur, 

 potassium, etc. have been supplied from outside. Thus a 

 seed will germinate although it has been soaked in 

 distilled water. The fact is that the seed contains a store 

 of food (the very store in fact which renders seeds valu- 

 able as food for animals), and when the young plant grows 

 it does so by the transference of part of this food to the 

 growing regions. The store is known as reserve material, 

 and the capability of accumulating reserves and of using 

 them by transference is one of great importance in the 

 lives of plants: it is for this reason that a chapter is 

 devoted to its study. 



The seed of the bean is covered by a smooth pale 

 leathery membrane called the testa or seed-coat, which 

 presents two special points of interest. At one end of the 

 seed, as shown in fig. 4, is a narrow elongated scar called 

 the hilum: it was at this point that the stalk grew by 

 which the bean was originally attached to the inside of 

 the bean-pod ; and it was through this stalk that the food 

 was transferred from the mother plant into the developing 

 seed. Near one end of the hilum is a hole known as 

 the micropyle which, when the seed was an ovule, 

 played an important part in the process of fertilisa- 

 tion. At present we need only note that it is 

 near the micropyle that the growing root escapes 



