268 BOTANY. 



flowers of the Aroids and Palms have a structure based 

 upon and but little modified from the lily type, while in 

 Grasses and Sedges are found the extreme modification and 

 simplification of the same type. From the Grasses 

 through the Sedges to the Lilies the gradation is an easy 

 one, while from the Orchids through the Irises the passage 

 is equally easy to the Lilies. We may, perhaps, regard 

 the Lilies as typical Monocotyledons from which the orders 

 diverge to specialized forms. 



507. The flowers of most grasses and sedges are wind- 

 pollinated (anemophilous), while those of the Orchids are 

 almost entirely dependent upon insects for pollination. In 

 the grasses we find a great amount of dry powdery pollen, 

 but in the Orchids, on the contrary, the pollen is in small 

 quantity and usually held together by sticky threads. The 

 stigmas of grasses are large, prominent, and generally 

 feathery, so as to easily catch and retain the pollen; in the 

 Orchids, however, they are mostly sticky surfaces, rarely 

 projecting, often much depressed. 



508. These differences in the sexual organs are accom- 

 panied by similar ones in the surrounding parts. Thus 

 the stamens and pistils in grass-flowers are surrounded by 

 chaffy scales pale or green in color. Such flowers are 

 therefore not conspicuous, although generally clustered at 

 the summit ot the stem. Moreover, they possess little or no 

 nectar, and, with few exceptions, are scentless. In the 

 Orchids there is a well-developed perianth which shows 

 high specialization of form and color. Most are provided 

 also with nectar-glands and an attractive odor. 



509. In Orchid-flowers the stamens and styles are fused 

 together into a "column" whicli occupies the centre of the 

 perianth. In the great majority of cases there is but one 



