PHANEROGAMIA. 245 
Order 32. The Orchids (Orchidacee) 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 (Burmanniacee) and Order 34, the Frog’s-bits (Hydro- 
charidez), 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, regard 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, 
