PKRIODICAL LITERATURE 1045 



counting for the presence of redwood, and that abundant precipitation 

 is sufficient in itself to make possible the development of the redwood 

 forest on mountain slopes. 



Many illustrations from field observations are presented to show that 

 tile redwood is unusually sensitive to the danger of water loss, evln 

 when the soil water supply is ample. On areas having abundant winter 

 precipitation, but little summer fog, redwood is excluded except in the 

 immediate vicinity of streams. This is probably due to the summer 

 desiccation of the soil and the high evaporation rate. 



The apparent effect of the summer fog is to. reduce the evaporation 

 rate and thus tide the redwood over the critical dry period of summer, 

 when there is little available moisture in the soil. The four stations 

 located in the fog-frequented area aroung Kings Mountain, although 

 covered with a heavy stand of redwood, gave a slightly lower precipi- 

 tation than the four stations in the fogless area of Black Mountain, 

 entirely devoid of redwood. 



The author's conclusion is: "For the full development of the red- 

 wood forest, covering mountain slopes which may become relatively 

 dry as well as the immediate environs of permanent streams, heavy 

 winter precipitation is necessary, but alone is not sufficient. Abundant 

 summer fog is also essential, its effects being to decrease the water loss 

 and in some degree add to the soil water supply. Where summer fogs 

 do not occur, or where they occur infrequently, no true forest of red- 

 wood is possible, even though the rainfall be as high or higher than in 

 the fog-frequented areas. In areas of the former kind the infrequent 

 redwoods were confined to the banks of streams, as in regions of de- 

 ficient precipitation." 



J. W. T. 



The Plant World, Vol. XX, June, 1917, pp. 179-189. 



SILVICULTURE, PROTECTION, AND EXTENSION 



In experiments by Davis on the resistance of 

 The Resistance seed-coats of velvet leaf (Abutiloii theophrasti) 

 of Seed-coats to the intake of water, the results indicate a re- 

 to the Intake markably wide range in the resisting power of the 

 of Water coats of these seeds to the absorption of water. 



The seeds were placed in vials of water and sub- 

 jected to various temperatures. Although some seeds were swollen 

 within three weeks after placing them in water, others of the same lot 



