36 



THE PLANT SOCIETIES OF 



and the poison sumach (Rhus venenata). Characteristic herbs, 

 especially in the open places, are the pitcher plant (Sarracenia pur- 

 purea^, the sundew (Drosera rotundtfolia), various orchids, as Calopogon 

 pukhellus, Pogonia, and Cypripediura ; sedges, as Eriophorum and 

 Dulichium ; Woodwardia Virginica, and Elodes campanulata. One of 

 the most typical plants of these places is the peat moss, Sphagnum. 



Fig 19. — Typical peat bog in a depression between established dunes at Miller. Relict of 

 the original pond at the left. Sedges (light-colored vegetation) are encroaching on the lake, 

 while slirubs, mainly Cassandra, are encroaching on the sedges. Cassandra islands toward the- 

 right. Advance of conifers on Cassandra (seen in its beginnings on the islands) shown at the 

 extreme right. 



The flora just mentioned has many interesting features, which are 

 well known and may be passed ovA briefly. The highly xerophytic 

 character of this plant society has already been noticed, and the rea- 

 sons for it briefly given. The xerophytic structures are well illustrated 

 in the leathery leaves of Cassandra and the absorption and storage 

 adaptations of Sphagnum. Many bogs of this type are very spongy 

 and unstable, whence the name quaking bogs; this feature is due to- 

 the rapid growth of the vegetation and the absence of ordinary inor- 

 ganic soils for a considerable depth. The similarity of the peat bog 

 vegetation throughout the northern hemisphere is one of its most 

 striking features. Not only the adaptations but the species themselves 



