CHAP, v.] RELATIONSHIP AMONGST PLANTS. 171 



dehiscence or opening of the fruit, as in the wood- 

 sorrel (Oxalis acetosella) and the geraniums. 



Important characters for classificatory purposes are 

 derived from the structure of the seed in Angiosperms. 

 Following the fertilization of the oosphere, important 

 changes take place in the ovule, one of which is the 

 accumulation of a certain amount of reserve material 



Fig. 52. Fruit of the maple, showing wing-like flattened expansions 

 for the purpose of effecting removal from the tree by the wind. 

 (Natural size. ) 



destined to serve as the first food for the young plantlet 

 on germination ; this arrangement is universal, as it will 

 be remembered that the assimilation of food depends on 

 the presence of green leaves, and the increase in size of 

 the tiny seedling up to the point of having leaves of 

 functional value is carried on entirely at the expense of 

 the material, known as endosperm, provided by the 

 parent plant. Contemporaneous with the appearance of 



