1886.] EDITORIAL NOTES. 539 



There are a few species of holly indigenous to North America, but 

 only one of them very nearly resembles our common holly which 

 with us and in northern Europe generally is regarded as the correct 

 thing wherewith to wreath Father Christmas. This American 

 substitute for our common holly is Ilex opaca, a species with flatter 

 leaves, but equally spiny, usually a little larger but not so deeply 

 green ; in short, it is not so fine a subject as the common holly for 

 the purpose, but is the only native product that may be used in the 

 place of our more showy sort. It grows in moist places along or 

 near the coast from Maine to Pennsylvania and Virginia southward ; 

 and at Christmas-time is distributed in great quantity throughout 

 the country from these regions, packed in long wide boxes, forming 

 rather an important item in the florists' trade at this festive season. 



The Influence of Forests on Climate. — In publishing the 

 results of many investigations on this subject conducted at many 

 differently situated stations on the Continent, Herr Woelkof draws 

 the general conclusion that in summer the earth and air of forest 

 areas are relatively lower in temperature, less variable, and more 

 humid than those of adjacent treeless regions ; and that in winter 

 the differences are trifling as regards humidity and temperature, but 

 that the forest still remains the least variable in the latter respect. 

 In a popular sense this conclusion has been held by our fathers and 

 grandfathers as the result of common observation, although it has 

 not perhaps been hitherto attested by careful scientific investigation. 

 It is observed that there is a very great difference in the degree of 

 evaporation that goes on in forests and continuous open areas. So 

 great is the influence of forests in diminishing evaporation from the 

 soil and the water within their areas as compared with open regions 

 lying close to them, that neither shade nor the lower temperature 

 and higher humidity combined are considered sufficient alone to 

 account for the disparity. Herr Woelkof considers the influence of 

 wind, which has not, he thinks, been fully appreciated in relation to 

 this matter, is the most important factor in producing this difference. 

 He is inclined, indeed, to ascribe to the absence of regular currents 

 and unimpeded atmospheric motion which prevails in forests more 

 power in limiting evaporation than is exerted by all the other 

 deterrent conditions combined. The resistance opposed to the wind 

 by masses of trees during the warm months prevents the rapid 

 absorption and removal of moisture from the forest area, while the 

 treeless tract is being parched by the currents which sweep 

 resistlessly over it from the forest. And to this immunity of 

 the forest from disturbing currents, and even from the effects of 



