Physiological Functions of riant Tissues. 269 



each of the two layers only communicate with each other 

 at certain points, so that the water vapour has to follow a 

 zigzag and devious course to leave the plant. The stomata 

 show a similar adaptation. In water plants and those not 

 exposed to much transpiration, they are level with or above 

 the surface ; while in tropical plants (and on the upper 

 surface only of the leaves of temperate plants), there is a 

 sort of chamber lying below the wind influence, above the 

 stomatic opening, and full of water vapour. 



Groivfh in Thickness of the Stem. — He shows that there is 

 a perfect transition in function between the various elements 

 of the xyleni. Thus there are libriform cells, or as he calls 

 them false tracheids, which have dotted canals, and conduct 

 water in addition to their primary mechanical function ; 

 thick-walled vessels, which are partly mechanical as well as 

 in his view water canals; also woody parenchyma cells, which 

 are partly mechanical, though their chief function is to 

 convey the carbohydrates ; and again vascular fibrous cells 

 (Ersatzfaserzellen), each of which is really a group of woody 

 parenchyma cells, which has not developed septa. 



Notes of a Visit to North America, as Delegate to the British 

 Association Meeting at Montreal, and to the American 

 Association at Philadelphia, 1884. By W. Caldwell 

 Crawford. 



(Read March 12, 1885.) 



(Ahstract.) 



Last summer the Council of this Societ}'' appointed the 

 author to be their delegate at these meetings, and his chief 

 object in presenting these notes is to thank the Society 

 for doing him that honour. 



I arrived in Canada in the middle of August, landing 

 at E-imouski, on the St Lawrence ; and travelling along 

 the railway to Kiviere du Loup, I got my first impressions 

 of American vegetation. The sides of the railway track 

 were bright with Impatie.ns fulva, a species not belonging 

 to Europe, although it has established itself here in a few 

 places. I then crossed the St Lawrence, and sailed up 

 that beautiful half river, half fiord — the Saguenay — for a 

 hundred miles or more. Here I made my first acquaint- 

 ance with Canadian forest scenery. The hills slope right 



