NOTES AND ABSTRACTS. 



391 



The leaves of these evergreen Ericaceae were able to absorb water from the 

 atmosphere, especially on frosty nights and at times of high relative humidity. 

 The scale-covered Chamaedaphne and Picea Mariana absorbed respectively 

 more water (per unit volume of leafy twig) than other evergreens and than Larix. 



Such absorption is not infrequently three or four times as great as the 

 loss by transpiration during a very cold winter day. Hence the advantage to the 

 plant is great when the ground is frozen solid. 



The relative rates of transpiration amongst evergreen Ericads varied 

 in the inverse order of their exposure and of their xerophytic structure. 

 Chamaedaphne, the most xerophytic, has the lowest rates of transpiration and 

 of conduction. 



In a very severe winter those leaves and branches of this plant which were 

 not covered by snow were killed. 



Transpiration appears to regulate, both absorption and conduction of 

 water, but only in a general way, and not exactly. The rate of conduction was 

 faster from warm solutions, but was never zero when the solution was frozen ; 

 it was much higher in summer than in winter, and was much less in the Ericaceae 

 than in other shrubs or herbaceous plants. The evergreen bog-tree Picea 

 Mariana had a lower rate of water conduction than any other tree examined. 

 Transpiration, on the whole, varies with the evaporating power of the air — that 

 is, increases with an increase of temperature, with more movement of air, 

 and with a decrease in relative humidity ; it is greater in daylight (perhaps 

 through increased internal temperature). 



Many of the author's experiments were carried out with cuttings, though 

 pot plants were generally used. The rate of transpiration was obtained by 

 weighing the plants on a balance sensitive to 0*002 gram. 



Light regulates the movements of the stomata of peat-bog plants, but such 

 movements do not control the transpiration of these plants so directly as the 

 evaporating power of the air. 



The data regarding the condition of the stomata were obtained by Mollisch's 

 infiltration method (time taken for leaf to become translucent when wetted with 

 xylol). 



There are many other interesting points in this paper regarding transpiration 

 &c. of peat plants. — G. F. S. E. 



