1918] CURRENT LITERATURE 283 
Grasslands and forests of Washington.—A recent study by WEAVER” 
physiography and geology of the region, the results of quantitative studies of 
the principal physical factors involved are _Teported. Tempe rature, rainfall, 
t 
and reviewed in this journal, and the present more complete report only tends 
to confirm the conclusion that the differences of the rates of evaporation in the 
various plant communities are sufficient to be important factors in causing 
succession. The studies of soil moisture also show that this important factor 
varies in amount directly with the order of the occurrence of the various com- 
munities in the order of succession. Incidentally it may be noted that the soil 
of the Thuja association has a very high water holding caper y showing during 
the months of July and August a supply of “growth water” of over 4o per cent, 
thus providing for the development of the very complete mesophytism seen in 
this ci conifer forest. 
western conifer forests here show a succession from shrub of xerophytic 
thirscter through Pinus-Pseudotsuga, Larix-Abies associations to the luxuriant 
conifer forest composed almost exclusively of Thuja plicata. The secondary 
species of this forest are carefully considered, as well as the reforestation of 
cutover areas and 
The scrub formation dominated by Artemisia tridentata and the hydrarch 
succession from ponds and streams are described, but perhaps aside from the 
notes the most important and interesting community is the grassland termed 
“prairie-plains formation” and dominated by Agropyron spicatum and Festuca 
ovina. It presents seasonal aspects varying from rich grassy verdure during 
the comparatively moist spring and early summer, to the sere brown of the 
arid late summer. The soil moisture determinations show the gradual deple- 
tion of growth water from the surface stratum, where it exists in June to the 
depth of 5 ft., by the middle of August. The response to this distribution of 
moisture is seen in the luxuriant spring growth and early flowering of the com- 
paratively shallow rooted grasses which dominate the community, and the 
entire absence of late blooming grasses. It is also apparent in the develop- 
Balsamorhiza sagittata, Hieracium Scouleri, and Lupinus ornatus. This exten- 
sive root development has been carefully studied by the same investigator," 
* WEAVER, J. E., A study of the root systems of ean te of southeastern 
Wiican = Plant World 18:227-248; 272-292. figs. 18. 1915 
3 Bor. me 59:71-72. 1915. 
4 Weaver, J. E., A study of the vegetation of southeastern Washington and 
adjacent Tdaho, Univ. Neb. Studies 17:1-114. 1917. 
