v] POLLINATION AND FERTILISATION 71 



suffices for the requirements, or Salvia (Sage), where 

 two half-stamens achieve the end. In either case 

 the flower-mechanism for making use of the visits 

 of certain insects is a peculiarly perfect one. 



The pollen-grain itself is protected externally by 

 a wall often thick, variously sculptured, and coloured. 



Fig. 



14. Pollen-grain of Lilium Martagon, and its germination, 

 k = nucleus of the large vegetative cell of the polleu-tube : m- 

 small mother-cell of the antheridium : g = generative cells, or 

 male gametes. ( x 375.) (From Strasburger, after Guignard.) 



Within are found at the period of ripeness two cells, 

 each with a nucleus (Fig. 14). The larger cell is 

 styled the vegetative cell, and it takes no direct part 

 in fertilisation. The smaller is called the antheridial- 

 mother-cell. It consists of rather dense protoplasm 



