DISTBIBUTIOK OF PLANTS. 283 



of latitude. For this reason, the intertropical position of N< \\ 

 Holland must be restored to the remainder of this continenl : 

 — the northern part of Africa should, perhaps, be united with 

 the intertropical part ; — Madagascar, from the number af pe- 

 culiar species, maydeserve the rank of a distincl region, while 

 New Zealand is almost a blank in the geography of land 

 quadrupeds. 



On the accompanying map of North America, the ranges oi 

 several plants are delineated. It is to be considered merely a 

 sketch; as a large portion of the country has not ye1 been visited 

 by a botanist, anil even in those parts which are besl known. 

 observations are either unpublished, or too few to determine, 

 with exactness, the range of a single species. Under these 

 circumstances, we are forced, in some instances, to substitute 

 conjecture for fact. 



Tin southern boundary of the arctic plants. In the eastern 

 pari of this continent, these plants cannot descend lower than 

 lat l l 1 *. on account of the inferior altitude of the Alleghany 

 niountain> south of thai line. How low they descend od the 

 northern Amies is no! yet ascertained. — The following have 

 been observed at the stations indicated on the map. Rum/ex 

 digynus, Silent acaulis, Polygonum viviparum, Trisetutn sub- 



spirillum. tVr. 



The coloured portion represents a fragment of a belt, 

 beyond which certain plants cannot exist, and the irregulari- 

 ties and inflections into which it is thrown in this continent, 

 by the inequality of climate and elevation of the surface: 

 the transverse lines mark the cessation of certain species. — 

 Thus, a few species do not appear to extend west of the M- 

 leghanies; — others are confined to the summits of these 

 mountains, as Pinus pungensj Rhododendron Catawbiense, 

 li. minus, ffiphytteia cytnosa, Pachysandra procumb&u, jSeo- 

 nitum urn ■nullum, Galax iijilii/l/u. tyc. — westward of the Al- 

 leghanies, plants occur which do not reach the Atlantic: — 



