REPRODUCTION 109 



ing glory vine, bamboo, etc., it can be measured every day with 

 a ruler. Make and record such measurements night and morn- 

 ing for several kinds of plants. 



154. Reproduction. This is the ultimate function of 

 all plants. For many it is the final function of life, the 

 death of the old individual occurring with the formation 

 of the new individual. It is perhaps to be considered as 

 the final act of growth toward which all development 

 of the plant has been leading. 



155. In many of the lower plants, especially those 

 that are undifferentiated, reproduction is nothing more 

 than cell division followed by separation of the cells thus 

 produced. In the more differentiated plants, however, 

 we find certain cells set aside for reproductive purposes. 

 These may be at first ordinary vegetative "cells that 

 later take up the reproductive function, or they may be 

 destined for the latter from their beginning. 



156. Very early in the vegetable and animal kingdoms 

 two types of reproduction become recognizable, the 

 asexual and the sexual. The former consists essentially 

 of the division of the plant, or of the separation from it 

 of single cells or groups of cells or even whole plant 

 members. By further growth these parts thus pro- 

 duced become like the parent plant. Not to be confused 

 with true asexual reproduction, is the development 

 of the gametophyte from the spores produced by the 

 sporophyte. 



157. Sexual reproduction is fundamentally different 

 from asexual reproduction in that there is requisite the 

 union of two distinct cells (or at least their nuclei) to 

 form a single cell, the zygote. This may develop 

 directly into a new plant or into a mass of cells (the 

 spore fruit), which produces only eventually the repro- 

 ductive cells, which give rise to the new plants. The 



