226 PLANT LIFE 
structure, the prothallus, on which the gametes 
are ultimately produced. 
It is, however, impossible to appreciate the 
significance of all this without some prelimin- 
ary acquaintance with the behaviour of the 
cell nucleus, and its relation to cell division 
and cell organisation, which will form the 
subject of the following chapter. 
CHAPTER XX 
THE CELL-NUCLEUS AND FERTILISATION 
In order to be in a position to grasp the 
essential facts of fertilisation, and their far- 
reaching consequences on the organism in 
general, it is necessary, as stated in the con- 
cluding paragraph of the preceding chapter, 
to learn something of the structure of the 
nucleus. Moreover, a study of the nuclear 
processes will enable us to apprehend the 
meaning of some of the most constant and 
singular features which, in the form of alterna- 
tion of generations, are of such widespread 
occurrence in the vegetable kingdom. 
