236 PLANT LIFE 



formed at meiosis often separate as four 

 spores, each of which may give rise to a new 

 plant destined in time to produce gametes. 

 Thus meiosis in plants has come to be asso- 

 ciated with a special kind of reproductive 

 multiplication which is sometimes called 

 asexual reproduction. 



It would be better to replace the terms 

 sexual and asexual reproduction by the terms 

 gametic and meiotic reproduction, and thus 

 do away with a misleading antithesis. For 

 " asexual " and " sexual " reproduction are 

 parts of one process, carried through in two 

 stages. The two phases of reproduction, 

 gametic and meiotic, in all the higher plants are 

 associated with two distinct stages in the life 

 history. One of these begins with the fertilisa- 

 tion of the egg, and ends in the meiotic 

 divisions. The spores, which are formed as 

 the result of meiosis, inaugurate the second 

 stage of the life history in which the differ- 

 entiation of sexual cells takes place. 



This rhythmic alternation of a spore-pro- 

 ducing with a gamete-producing generation 

 is well illustrated by the fern. Starting with 

 the fertilised egg, an embryo is produced, 

 which grows into the ordinary fern. If the 

 backs of the leaves are inspected, brown spots 

 or stripes may often be seen, and these are 

 found to consist of small capsules or spor- 

 angia. A young sporangium contains a fairly 

 definite mass of internal cells which are 

 enclosed by nutritive tissues, the whole being 



