THE NORTH TEMPERATE ZONE 91 



showy herbaceous flowers occur in this district. Of the orchids, the 

 most beautiful is the pink lady's slipper, or " moccasin-flower, ' 

 Cypripedium acaule. 



The northern Xew England coast, owing to its rocky forma- 

 tions, and great differences in tide levels, offers exceptional 

 opportunities for the study of the rich marine flora, much of 

 which is exposed at low tide. The vertical rock faces show an 

 interesting succession of forms, the light green sea-lettuce (Ulva), 

 appearing near the high tide mark; below this, but exposed 

 for much of the time are several bladder kelps (Fucus spp.) and 

 the curious Ascophyllum nodosum, whose long whip-like fronds 

 form a dense curtain along the base of the rocks, and parti} 

 conceal the bladder kelps. With these large sea-weeds are asso- 

 ciated many smaller species of red and brown algae. 



Below the low-water mark is a region with a great develop- 

 ment of the large kelps, Laminariaceae, in which several species 

 of Laminaria predominate. Other characteristic species are 

 Alaria esculenta and Agarum Turneri. The more delicate red 

 algae are found mostly at still greater depths. 1 



Throughout most of New England the American elm (Ulmus 

 Americana), is a very characteristic tree, reaching perhaps its 

 finest development in the Connecticut valley. Red and white 

 oaks, white pine, walnut and hickory are abundant, and until 

 it was completely exterminated by the blight, the chestnut 

 (Castanea dentata) was one of the commonest trees of New Eng- 

 land. 



In southern Connecticut, near the shores of Long Island Sound, 

 the tulip-tree and sweet gum (Liquidambar) are found, but these 

 trees belong more to the regions further south. 



From the St. Lawrence to the Lower Lakes, including western 

 New York, southern Michigan and Ontario, is a forest region 

 which has few or no coniferous trees throughout much of its 

 extent, although in some districts hemlock and white pine occur. 

 Further north, in northern Michigan, Wisconsin and Minnesota 

 the forest is predominantly coniferous, but there is a consider- 

 able mixture of deciduous trees. The most important tree of 

 this northern forest is the white pine (Pinus slrobits), which 

 has been largely exterminated by the lumberman. The white 



1 For a fuller account of these algae, see Harshberger, loc. cit., pp. 383-1. 



