CHAPTEE VI 



REPRODUCTIVE ORGANS 



It will be remembered that nutrition and reproduction 

 are the two great functions of plants. In discussing 

 foliage leaves, stems, and roots, they were used as illustra- 

 tions of nutritive organs, so far as their external relations 

 are concerned. We shall now 

 briefly study the reproductive 

 organs from the same point 

 of view, not describing the 

 processes of reproduction, but 

 some of the external relations. 



71, Vegetative multiplica- 

 tion.— Among the very lowest 

 plants no special organs of 

 reproduction are developed, 

 but most plants have them. 

 There is a kind of reproduc- 

 tion by which a portion of 

 the parent body is set apart to 

 produce a new plant, as when 

 a strawberry runner produces 

 a new strawberry plant, or 

 when a willow twig or a grape 

 cutting is planted and produces new plants, or when a potato 

 tuber (a subterranean stem) produces new potato plants, or 

 when pieces of Begonia leaves are used to start new Begonias. 

 This is known as vegetative multiplication, a kind of repro- 

 duction which does not use special reproductive organs. 



109 



B 



Fig. 106. A group of spores : .4, 

 spores from a common mold (a 

 fungus), which are so minute and 

 light that they are carried aboat by 

 the air ; B, two spores from a com- 

 mon alga ( XTlothrixX which can 

 swim by means of the hair-like 

 processes; C. the conspicuous dotted 

 cell 18 a spore developed by a com- 

 mon mildew (a fungus), which ia 

 carried about by currents of air. 



