= BOTANICAL GAZETTE [FEBRUARY 
matter, thus adopting a plan which ENGLER had previously adopted in the 
Pflanzenreich. 
ollowing the preface is a German summary of the contents of the volume 
by Drupe. Part I gives a survey of floristic and phytogeographic work in 
North America, and also a most useful bibliography. Part II contains an 
account of the geography and climate of the continent, together with some 
plant statistics. Part III has to do with the geologic evolution of the North 
merican flora from the Cretaceous to the present. Here there are discussed 
the sudden appearance of Cretaceous angiosperms, and the influence of Pleis- 
tocene glaciation in the destruction of species and in the production of relict 
endemism. A detailed account is given of the postglacial history of our flora. 
To the north there has been a succession of forest types, culminating in the 
dicotyl forests which now generally dominate. Interesting accounts are given 
of recent changes in the vegetation of the coastal plain. HARSHBERGER aligns 
himself with those who regard the prairies as sufficiently explained by taking 
account of historical factors. This part closes with a description of the affinities 
of the North American flora and a list of phytogeographic classifications per- 
taining to North America. 
Part IV, which comprises more than half of the volume, presents in some 
detail the phytogeographic regions of North America, and is accompanied by a - 
colored map which makes it easy to follow the text. There are seven chapters, 
dividing the continent into as many “zones”: (1) The arctic and subarctic 
zones; the latter is subdivided into the Labrador, Hudson Bay-Keewatin, 
Mackenc and Alaska districts. (2) The North American temperate zone, 
Atlantic ee subdivided into the St. Lawrence—Great Lake, Atlantic—Gulf 
Coast, and Piedmont-Appalachian-Ozark regions. Among the districts most 
fully treated are New Brunswick (based largely on GANONG’s studies), the New 
England mountains, the Adirondacks, the New Jersey pine barrens, the coastal 
formations, and the various forest districts. (3) The North American tem- 
can tropic zone, Mexican and Central American section. (7) The North 
American tropic zone, West Indian section. The illustrations are good, but 
are much too few to depict properly the vegetation of a continent —HENRY 
C. COWLEs. 
NOTES FOR STUDENTS 
Cecidology.—The similarity of plant galls and animal tumors is attracting 
the attention of workers in various parts of the world. Saut? has issued a 
preliminary paper in which he expresses the opinion that some of the various 
2 Saut, E., Beziehungen der Acari zur Geschwulstatiologie. Centrabl. f. Bakt., 
Paras., und Infekt. 59:400-406. 1grt. 
