1918] CURRENT LITERATURE 287 
upon many of the steep slopes is termed “‘ Fynbosch”’ and described as a sclero- 
phyllous formation comparable to the chaparral of the United States. It is 
dominated by shrubs with needle and ericoid leaves, conspicuous among which 
are the genera Cliffortia (Rosaceae) and Erica, both represented by several 
species, and a large number of woody Combeatine. In its undergrowth, bulbous 
i “bush” 
or forest, in which Podocar pus spp. and Celtis Kraussiana are the most abundant 
trees, the other to the mountain veld. e former is clearly leading to the 
climax type of tree vegetation developing only under the most favorable condi- 
tions of soil and exposure; but the succession in the latter instance does not 
seem clear, for the veld is apparently more xerophytic, although more extensive 
than the “ Fynbosch.”—Gero. D. FULLER 
Germination of tree seeds.—BOrERKER* has carried on three series of 
greenhouse cultures to determine the effect of light, soil moisture, and soil 
texture upon the germination of the seeds of various forest trees. The 
cultures were extensive and the environmental factors rather carefully con- 
trolled. The variations in response are too numerous to be touched upon in a 
review, but some items of the summary show that it has not been possible to 
isolate the effect of single factors, as it is stated that shade accelerates germina- 
tion and this acceleration is due to increase in soil moisture caused by decreased 
evaporation and transpiration. On the other hand, light is found to play 
absolutely no part in the germination of tree seeds. Similarly, the differentia- 
tion between the effects of soil moisture and soil texture has not been accom- 
plished. 
The reaction of different tree species to the different sets of conditions is 
interesting, and the results should be of practical service to foresters. The 
increase of length of tap and lateral roots in Pinus ponderosa with diminishing 
soil moisture content may be cited as one of the results. P. ponderosa growing 
in the Rocky Mountains produces smaller seeds that germinate more quickly 
than those from the same species grown upon the Pacific coast. Similar dif- 
ferences were found for local varieties of Pseudotsuga taxifolia; while in both 
Species large seeds proved superior to small, both in higher germination per- 
centage and in the size of the seedlings.—Gro. D. FULLER. 
L e minimum.—HOookeEr’* gives an interesting discussion on the 
application of the law of the minimum, or limiting factors, to biological prob- 
ems. He is perhaps fortunate, in so far as rigid application of the law is con- 
cerned, in drawing his early illustrations from simple chemical and physical 
Processes, for it is rapidly becoming a question whether the law applies to plant 
eats 
Bor , R. H., Ecological investigations upon the germination and early 
growth of ery trees. Sra. pp. 89. pls. 5. Thesis Univ. Nebraska. 191 
3S Hooker, D. H. , Liebig’s law of the minimum in relation to ee biological 
problems, Sais S, 46:197-204. 1917. 
