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 : CHORIPETAL^E 



The Dicotyledons may be divided into two pretty well- 

 defined great divisions, each of which contains numerous 

 orders. In the lower series (Choripetalse), the petals 

 are quite separate, and this may be true of other parts 



