148 



BREEDING 



The pea, as has been already stated, is self- 

 fertilised. Fertilisation occurs before the flower 

 has opened. The fact that a flower is open is a 

 certain sign that fertilisation has taken place. 

 Fertilisation occurs in the following manner : At a 

 stage in the development of the flower, shown in 

 Fig. 31, i.e. long before the flower has opened, in 

 fact whilst its petals, the only one 

 of which to be seen at this period 

 is the folded standard, are still of 

 a greenish colour, the anthers burst 

 and the pollen grains escape into the 

 space enclosed between the two 

 halves of the carina. In the centre 

 of this space lies the pistil, so that 

 it at once becomes surrounded with 

 an immense number of pollen grains. 



— otage in 



when fertilisa- 

 tion occurs. 



the development rj.j^^ ^^^^ rcproductivc ccUs in the 



or the rlower ■»- 



pollen grains reach the ovules in the 

 following way. Some pollen grains 

 stick to the free end of the pistil, and each one 

 of them sends out a structure, known as the pollen 

 tube, which grows like a root into the tissue of the 

 pistil and travels dow^n it until it reaches one of 

 the ovules. This pollen tube contains the male 

 reproductive cell, and when this has fused with an 

 ovule, the ovule proceeds to develop. 



When, therefore, it is desired to make a cross 

 between two kinds of peas, it is necessary to select a 

 flower, on the plant which is to function as the female 

 parent, of such an age that the anthers have not 



