CHAPTER XVIII 



THE PHYSIOLOGY OF REPRODUCTION 



Necessity for Reproduction. Hitherto the means by 

 which plants maintain their individual lives have alone been 

 considered. The limited duration of the life of a single plant is 

 known to every one. Plants are not only preyed upon by slugs, 

 but larger animals also use them for food, and countless parasites, 

 too, live on them. Plants also struggle among themselves for 

 food and light. Extremes of cold and heat have to be con- 

 tended with. Plants live, die, and new ones take their place. 

 Given this fact that plants die, the subject of reproduction 

 becomes of vital interest, because it is the only way as far 

 as is known by which these new individuals can be produced. 

 All existing plants are the descendants of ancestral forms. 



By reproduction is meant the production of new individuals by 

 an existing plant. This can take place in two ways : (i) By a 

 portion of the vegetative part of a plant being cut off from the 

 parent plant, thus forming a new individual. This method 

 of reproduction is called asexual or vegetative reproduction. 

 (2) By the union of two cells, one the male, the other the female. 

 These cells, by their fusion, form a single cell which is capable of 

 developing into a new individual. This method of reproduction 

 is called sexual reproduction. 



Vegetative Reproduction. This form of reproduction is 

 comparatively simple, and almost any part of the plant may 

 become separated to form a new individual. The branches of 

 the Gooseberry bend down, and roots are formed at the ends of 

 the branches, which become detached, and form independent 

 plants. The runner of the Strawberry creeps over the surface 

 of the soil for a considerable distance, and roots develop at its 



