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TEXTBOOK OF BOTANY 



The flowers of orchids are remarkable as to both form and attractive- 

 ness (Fig, 339). The three sepals are either green or the same color 

 as the corolla. Two of the three petals are "wings." The third petal is 

 below the other two and may be inflated, spurred, or variously shaped; 

 it is known as the "lip." The masses of pollen and the lobes of the stigma 



Fig. 339. Unique flowers of a cultivated orchid (Cypripedium) . 



are often viscid, and this along with structural modifications facilitates 

 pollination by certain insects. 



The fruit is a capsule, and the tiny seeds have an undifferentiated 

 embryo, but no endosperm. Some 700 genera and nearly 15,000 species 

 of orchids have been described. The plants are cultivated for their mag- 

 nificent flowers ( Fig, 340 ) . 



The willow family (Salicaceae) . The willows and poplars constitute 

 this family; although widely distributed throughout the world, they are 



