iQ2o] CURRENT LITERATURE 447 



baceous vegetation with increasing altitude is due to increased soil moisture 

 and decreased rate of evaporation. 



An analysis of the foliage shows that leaves with entire margins are more 

 abundant in the lower stories than in the upper, and at lower elevations than 

 at higher ones. Classified according to the system devised by Raunkiaer, 

 the plants over a meter in height are found to show but three leaf sizes, and 

 the number of species with microphyll, mesophyll, and macrophyll leaves are, 

 for the most part, Dipterocarp forest, respectively 4 : 79 : 9; for the mid-mountain 

 forest 4:61:5; and for the mossy forest 8:8:0, showing a decided decrease in 

 leaf size with increase in elevation. 



The Philippine vegetation is made more attractive to the reader by 

 numerous good photographs reproduced on excellent plates. — Geo. D. Fuller. 



Transpiration studies. — A series of papers by Sayre 9 contains some 

 interesting results regarding transpiration from hairy leaves. The leaves of 

 the mullein, Verbascum Thapsus, offer more resistance to water loss in dark- 

 ness than in light, in still air than in wind, and respond rather more to changes 

 in environment than do the smooth leaves of tobacco, Nicotian a sp. The 

 removal of the hairs of the mullein leaves resulted in no change of resistance 

 in still air and light, and but slightly reduces resistance in wind and light. 

 There was a greater reduction of resistance to water loss caused by the removal 

 of hairs in still air and darkness, as under such conditions transpiration is 

 entirely cuticular. Hence it appears that, in this plant at least, hairs as a 

 covering affording protection against ordinary intensities of wind and light 

 are quite inefficient and may be disregarded. The stomatal water loss is 

 20-40 times the cuticular, and only the latter is influenced by the removal of 

 the hairs. 



Transpiration, humidity, evaporation, and sunshine were recorded along 

 with the water loss from sealed potted plants. Stomatal transpiration is shown 

 to be governed by various factors which control the opening and closing of the 

 stomatal pores, and by the diffusion gradient. An increasing saturation 

 deficit of the intercellular spaces of the mesophyll is regarded as important in 

 increasing the resistance of the leaf to water loss while stomata are open, but 

 as of no effect after stomata are closed by darkness. 



The tobacco and Verbascum Thapsus show a rhythm in the transpiration 

 curve in darkness for one day only succeeding a day of normal light exposure, 

 but V. Blattaria exhibits no such rhythm under the same conditions. 



Geo. D. Fuller. 



9 Sayre, J. D., Comparative transpiration of tobacco and mullein. Ohio Jour. 

 Sci. 19:422-426. fig. r. 1919. 



, Factors controlling variations in the rate of transpiration. Loc. cit. 



19:491-509. figs. 9. 1919. 



, The relation of hairy leaf coverings to the resistance of leave- to transpi 



ration. Loc. cit. 20:55-75. fig. 7. 1920. 



