PBANBllOOAMlA. 245 



Order 33. The Orchids (Orchidacese) constitute an immense group 

 of 4500 to 5000 species of perennial herbs. Some of these are terres- 

 trial, while very many are epiphytic (i.e., grow upon trees: not para- 

 sitically, however). 



Order 33 (Burmanniacese) and Order 34, the Frog's-bits (Hydro- 

 charidese), include about 100 species of small herbs. 



515. The Monocotyledons include many of the most in- 

 teresting plants botanically to be found in the vegetable 

 kingdom. While the flowers in the lower orders are sim- 

 ple and unattractive, those in the higher series are often 

 exceedingly complex and of great beauty. If, for exam- 

 ple, we compare the flower of a grass with that of an Orchid, 

 the differences are so great that at first we can scarcely see 

 any resemblance. However, the two stand at opposite ex- 

 tremes, and, as may be seen by a study of the foregoing 

 synopsis, there is a pretty regular gradation from the one 

 to the other. From the Grasses through the Aroids to the 

 Palms the gradation is an easy one, while from the Orchids 

 through the Irids the passage is equally easy to the Lilies. 

 We may, perhaps, reg'ard the Palms and the Lilies as typi- 

 cal Monocotyledons between which lie a number of small 

 connecting orders, and from which on either hand the 

 orders diverge to specialized forms. 



516. While the flowers of most grasses are wind-pol- 

 linated (anemophilous), 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. 



