DICOTYLEDONS 205 
the stem and leaves. These thick protective tissues also 
serve to shield the underlying green cells from the too 
strong rays of the sun. The latter result is also brought 
about in many desert plants by the development of a 
thick covering of hairs to which the peculiar gray color 
of many of these is due. 
Dicotyledons are among the last plants to disappear 
upon high mountains, and some of them have been 
encountered as far toward the poles as explorations have 
extended. 
Among the Dicotyledons are found the most extraor- 
dinary modifications known among plants, such as the 
remarkable contrivances developed in some of the insec- 
tivorous plants like the pitcher-plants and the Venus’s 
fly-trap. It is among these also that the most perfect 
types of climbing plants are found, especially those with 
tendrils of various patterns. Parasites and saprophytes 
are common in certain families of Dicotyledons, while 
among the Monocotyledons they are rare. The mistle- 
toe and dodder are familiar examples of parasites, while 
the Indian pipe of the eastern United States, and its 
near relative the curious “snow-plant” (Sarcodes) of 
the Sierra Nevada, may be cited as typical saprophytes. 
Everywhere, except in the sea, where any vegetation 
exists at all, we encounter the ubiquitous Dicotyledons. 
CLASSIFICATION OF DICOTYLEDONS: CHORIPETALZ 
The Dicotyledons may be divided into two pretty well- 
defined great divisions, each of which contains numerous 
orders. In the lower series (Choripetale), the petals 
are quite separate, and this may be true of other parts 
