1gto} CURRENT LITERA TURE 383 
SPALDING concludes that even in deserts soils play a great part in distribution, 
and that physiographic factors play an efficient part as in the East 
as the region is gradually base-leveled, the area of the mesquite association 
widens, that the palo verde-catclaw association advances similarly along the 
washes, and that the creosote bush advances along the slopes. The latter species 
is of wide range, appearing in areas as a pioneer and also remaining as the final 
possessor; and yet the xerophytic structures of this plant are simple as compared 
with the spectacular features of the giant cactus, whose range is much more 
restricted. The soil factors that appear most important are the soil water content, 
the percentage of alkali, and the soil texture (involving aeration). That not all 
distributional factors reside in the soil is shown by the fact that the giant cactus 
is chiefly an inhabitant of south slopes (attributed to the need for high tempera- 
tures), and especially by the fact that Lippia Wrightii is restricted to the north 
slope about the laboratory, while it is just as definitely restricted to the south 
slope in the mountains at an altitude of 1000™ above the laboratory. SPALDING 
has here given us one of the most notable of recent contributions, clearly showing 
that the intensive study of plant associations is quite as productive in results in 
deserts as in mesophytic climates.—H. C. Cow es. 
Evolution 
It is a matter for congratulation when the subject-matter of any great field is 
gathered together and systematized by a master hand. The first volume of 
Lorsy’s lectures on the theories of descent has been reviewed in these pages, and 
the second volume should have been noticed sooner.4 -The first chapters of the 
second volume consider various phases of Darwinism, noting first the factors that 
influenced Darwrn’s investigations. The various prerequisites of Darwinism, 
Such, as variability, selective value, and the struggle for existence, are first con- 
sidered. It is recognized that DARwiN did not attempt to explain variability, 
assuming it as given. Nor did DARWIN distinguish sharply between variations 
and mutations, a view that seems to the author to be borne out by KiEss’s experi- 
ments. After lectures on orthogenesis, selective value, the struggle for existence, 
the inheritance of deviations, there follow several lectures on the facts of pale- 
ontology and plant geography that are explained by the Darwinian theory. The 
objections to Darwinism are considered, the matter of the isolation of deviating 
individuals being considered one of the more important. The closing lectures 
eal with post-Darwinian theories, notably those of WaLLacr, NAGELI, and 
DeVries, while one lecture is devoted to Neolamarckism. At the close is an 
of information, not alone to students of evolution, but to all biologists, and particu- 
3 Bot. GAZETTE 42:60-61. 1906. 
Lorsy, J. P., Vorlesungen iiber Descendenztheorien mit besonderer Beriick- 
sichtigung der botanischen Seite der Frage, fag ree an der Reichsuniversitat zu 
iden, sie Teil. 8vo. pp. vit+420. pls. 13. figs. 101. Jena: Gustav Fischer. 
1908. M1 M 
