PROCEEDINGS OF SOCIETIES. 93 



nortlierly winds at Malta are peculiarly characterized by excessive cold 

 and dryness. On the other hand, its proximity to Africa exposes it in 

 summer to scorching- blasts of heated air. These drawbacks are felt in 

 tlieir fullest extent, owing to the almost complete absence of trees on 

 tlie island. The influence of forests on climate has been made a subject 

 of investigation by meteorologists of late years, and though much still 

 remains to be done, yet some important points have been established. 

 The highest temperature of the air occurs in summer between two and 

 three p.m., but trees do not attain their highest temperature till 

 nine p.m. Changes of temperature take place slowly in tlie tree, but in 

 the air they are rapid. Hence trees may be regarded, like the ocean, as 

 powerful equalizers of temperature, in moderating the heat of the day, and 

 in maintaining a higher temperature during tlie night. Since air is heated 

 by contact with the soil, and since trees shield the soil from solar radia- 

 tion, it is evident that trees diminish the force of the sun's rays, especially 

 in the lower stratum of the atmosphere, which is breathed by man. Trees 

 exhale moisture, and thus produce cold in the air by the latent heat ab- 

 stracted from it. From this lowering of the temperature, and from the 

 moisture which is exhaled, dry winds acquire greater relative humidity, 

 and thus are deprived of much of their noxious influence; and since trees 

 break the force of the wind, their beneficial influence is greatly augmented. 

 During night the process of terrestrial radiation lowers the temperature of 

 a tree at a slow rate. First the upper leaves are cooled, then tliose leaves 

 immediately under, and so on, until the whole are cooled. Nov\^ in the 

 earlier part of the day, before the tree is heated by the sun, its cool leaves 

 present a very large surface to the air currents which pass through them. 

 Hence tlie cooling influence of trees is very considerable, which all must 

 have experienced in the deliciously cool breezes of well-planted parks on 

 a warm summer day. This refrigerating influence of trees is sometimes 

 well seen in the earlier part of the day, when the air is filled with fog. 

 In such cases heavy drops of water fall from the trees and increase, on 

 occasions, to the copiousness of a heavy shower; and, doubtless, when 

 the air is saturated, the rainfall will be heavier when the wind advances 

 on a forest, whose temperature is several degrees lower than that of the 

 surrounding district, where there are no trees. Hence, then, it may fairly 

 be inferred, if it has not been indeed proved, that trees bring about a 

 different distribution of the rainfall, as respects the time of the day and 

 tiie season of the year. Trees serve another important use. When rain 

 falls on so dry and bare a soil as that of Malta, it runs ott" at once, and is 

 lost in useless, if not destructive floods. But since the roots of trees 

 penetrate the soil, and so loosen it, and render it porous, much of the ram 

 is not only received and preserved by the trees, but what falls tq the 

 ground is allowed to sink into the soil, and fill the reservoirs of the deep- 

 seated springs. And since, owing to the stillness and greater dampness 

 of the air among trees, the evaporation from forest soil is oidy about a 

 fifth of what it is in an open country, woods ngulate the flow, and retard, 

 if they do not altogether prevent the drying up of springs. — "Notes on 

 the Structure and ]\Ieasurements of Cells in the Uepnilcfe. l>y James 

 AVilliamson Edmond, M.B., CM. The author described the characters 

 and measurements of the leaf-cells of twenty-six species of British llepa- 

 tic(jP, he also gave the measurements of the spores and elaters of several 

 of the species. He considered that, owing to the great variation 



