PFLANZEN-GEOGRAPHIE AUF PHYSIOLOGISCHE GRUNDLAGE. 48 
like a look back into the dark ages, and one is not surprised to find 
that Najas flexilis is still the only British species of the genus 
W ed mo 
book, which we shall agen expect, Professor Vines should get 
a systematist to do the systematic account of seed-plants, and 
thereby recognize that tice kaicn of labour sdccame we were wont 
to learn in the old days, is a criterion of developmen 
B. BR. 
_— Geoyraphie auf a ae Grundlage. Von Dr. A. F. ma 
ScHimPE p- , 876, with 502 drawings and re 
are from t hetoeaglae 5 actieeeeds and 4 peograpliea 
maps. Jena: Verlag von Gustav Fischer. 1898. Price 27 m 
THE science of Regs is defined by Haeckel to be yi 
knowledge of the sum of the relations of organisms to the sur- 
cl 
the science of cecology to the vegetable kingdom, 
exceedingly important contribution to botanical literature, and the 
book will be eagerly welcomed and read by all who are in any way 
interested in oe nts. 
r treats his subject under three great divisions. In 
the first, ontitled ‘Factors,’ he discusses soil, temperature, light, 
&e., and, as of especial importance, the presence or absence of 
regions, to deser t lands, or to ger wet an ha dry seasons. The 
conditions that have developed these different classes of plants may 
be due to climate or to the state of the ground (adaptive influence), 
and these two influences may come into play in very close proximity. 
On the Suhara we should look mainly for Xerophytes, though here 
and there in the scattered oases we should find colonies of Hygro- 
h 
3 The second great section of the book deals with ‘‘ Formations 
and Associations.’’ These formations of —— kinds of vegetation 
du to th oe nee of climate and ground. Under 
succession with the tropics, the tempera and the arctic etal the 
plants that inhabit mountain regions, and water flora. In the 
tropics the periodic alternations of wet and et seasons, the intense 
sunlight and hot wind have all to be met by the plan ts with 
oe Lier sdatations In the arctic regions the 
¢ ; the plants have to encounter 
