411 



CHAPTEK XXV 



REPRODUCTION 



THE phenomena we have hitherto been considering all 

 concern the life of the individual plant. As this, however, 

 at the best is comparatively limited in duration, 'we find 

 plants possessed of the power of giving rise to new in- 

 dividuals. The process of originating each new individual 

 from its parent or parents is known as reproduction. 



We have seen that the life of the plant is essentially 

 bound up with the individuality of the protoplasts which 

 compose it. Many plants consist of but a single one of 

 these organisms : others are composed of many, some of a 

 very large number. We have seen reason to look upon 

 each of these aggregations of protoplasts as a large colony 

 whose members have become differentiated in various 

 ways to carry out to the greatest advantage the vital pro- 

 cesses of all. In the simplest forms, such as filaments of 

 protoplasts like Spirogyra or Ulothrix, each protoplast is 

 apparently independent in its behaviour, though mechani- 

 cally attracted to its neighbours. In more complex and 

 bulky forms this independence has been given up in favour 

 of complete co-operation for the general welfare. 



As every plant, then, is composed of either one proto- 

 plast or many, we may in the latter case distinguish 

 between the colony and its constituents. The term 

 individual is usually associated with the former, and we 

 speak of reproduction as leading to the appearance of such 

 individuals without making any reference to the proto- 

 plasts of which it consists. In dealing with reproduction, 

 however, in the broad sense we must consider also the 



