30 



GENERAL PRINCIPLES. 



gtaminate flower of 

 the strawberry. 



FIG 



Fig. 36, flower of t 

 bert. 



(fig. 38) on another. The most familiar instance among 

 plants cultivated for their fruits, is the strawberry. In 

 many varieties we 

 find the stamens or 

 male organs so in- 

 completely devel- 

 oped (fig. 38) that 

 they are of no ser- 

 vice in fructifying 

 the flowers, and 

 hence we plant near 

 them varieties with an abundance 

 of these organs strongly exhibited. 



3d. Impregnation. 

 The process of im- 

 pregnation is effected 



in this way : "When the flowers first open, 

 the pollen granules or powder in the anthers, 

 is covered over by a delicate membrane. 

 In a short time this membrane bursts in a manner similar 

 to an explosion that scatters the pollen by its force, so 

 that it reaches the stigma of the pistil ; this is composed of 

 glutinous or sticky secretions to which the pollen adheres ; 

 there it forms new cells that expand into tubes ; these 

 tubes penetrate through the style of the pistil to the ovary, 

 where the impregnation takes place, and new cells are 

 immediately formed into an embryo plant. 



This impregnation is sometimes, from certain causes, 

 only partially effected in the cases of fruit where the ova- 

 ry or seed vessel is composed of several cells, as in the 

 apple, pear, &c., and hence the fruit takes an imperfect, 

 one-sided development from the beginning. 



The difficulty that appears to arise in the way of the 

 impregnation of the stigma of one flower by the pollen of 



FIG. 38 



Fig. 38, female 

 or pistillate flow 



