318 HOW CROPS GROW. 



On the other hand, the reversion of all the floral • 

 organs into ordinary green leaves has been observed not 

 infrequently^ in case of the rose, white clover, and other 

 plants. 



While the complete flower consists of the four sets of 

 organs above described, only the stamens and pistils are 

 essential to the production of seed. The latter, accord- 

 ingly, constitute a perfect flower, even in the absence of 

 calyx and corolla. • 



■ The flower of buckwheat has no corolla, but a white or 

 pinkish calyx. 



The grasses have flowers in which calyx and corolla are 

 represented by scale-like leaves, which, as the plants ma- 

 ture, become chaff. 



In various plants the stamens and pistils are borne on 

 separate flowers. Such are called moncBcious plants, of 

 which the birch and oak, maize, melon, squash, cucum- 

 ber, and often the strawberry, are examples. 



In case of maize, the staminate flowers are the "tas- 

 sels" at the summit of the stalk; the pistillate flowers 

 are the young ears, the pistils themselves being the 

 " silk," each fiber of which has an ovary at its base, that, 

 if fertilized, develops to a kernel. 



Dioecious plants are those which bear the staminate 

 (male, or sterile) flowers and the pistillate (female, or • 

 fertile) flowers on different individuals ; the willow, the 

 hop-vine, and hemp, are of this kind. 



Nectaries are special organs — glands or tubes — secret- 

 ing a sugary juice or nectar, which serves as food to 

 insects. The clovers and honeysuckles furnish familiar 

 examples. 



Fertilization and Fructification. — The grand func- 

 tion of the flower is fructification. For this purpose 

 pollen must fall upon or be carried by wind, insects, or 

 other agencies, to the naked tip of the pistil. Thus sit- 

 uated, each pollen-grain sends out a slender microscopic 



