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CHAPTER IX. 



CELLS HAVING THE FUNCTION OF REPRODUCING 

 THE SPECIES. 



In this chapter a very important subject will be dealt with — 

 viz., reproduction — and it will be found convenient, to start 

 with, to examine the reproductive cycles as they occur in the 

 three great groups of the Higher Plants — i.e., Augiosperms, 

 Gymnosperms, and Pteridophyta. In all these, certain primary 

 essential cells arise in special organs, the reproductive organs. 

 Thus, in Angiosperms and Gymnosperms, the male cells, or, as 

 they are usually termed, the microspores or pollen-grains, arise 

 in the anthers of the stamens of a flower; and the female cell — 

 viz., the macrospore or embryo-sac — is formed in the nucellus of 

 the ovule, or sporangial portion of the flower. These two 

 elements, the microspore and macrospore", undergo, first of all, a 

 process known as maturation, in which certain cells are formed 

 in each structure ; one of these cells, in each of the fully matured 

 sexual elements (microspores and macrospores) being the 

 effective cell, which, by fusion with its counterpart, results in 

 the production of a fully-fertilised cell, from which the embryo- 

 plant is reproduced. 



Thus, to put the process into tabular form, the following 

 stages are noted : — 



-> Microspore 

 $ Effective cell 



Macrospore <- 



i 

 § Effective cell 



Fertilised cell 



Embryo-plant 



= spore-forming or asexual generation. 



