10 SEA MOSSES. 



marked difference in temperature, in the two regions. 

 At all events the floras of the two regions have im- 

 portant differences, whatever the cause. I do not mean 

 by this that no considerable number of species 

 extend over the whole region, north and south of 

 Gape Cod. But I mean that a considerable number, 

 enough to make a distinct feature of the flora, do 

 not extend either way beyond that barrier. To state 

 it broadly, we may say that the plants growing north 

 of Cape Cod are essentially arctic, and agree pretty 

 well with the species found on the extreme northern 

 coasts of Europe, and in Spitsbergen and Nova Zembla. 

 In a small collection of some twenty species received 

 from these polar islands, I find all but one or two of 

 them such as I have collected at Marblehead. The 

 individual plants, too, have a striking resemblance to 

 those growing along our northern shores. The north- 

 ern flora is distinguished by an abundance of plants of 

 the species Euthora cristata, Ptilota plumosa, Var. 

 serrata. Ceramium Deslongchampsii, Gigartina mam- 

 illosa, Halosaccion ramentaceum, Fucus furcatus, 

 Agarum Tumeri, Laminaria longicruris, Alaria 

 esculenta, etc. 



The flora south of Cape Cod is that of the warmer 

 or temperate seas, and is distinguished by the presence 

 of such forms as the " Gulf weed," Sargassum vulgare. 



