f\ 



1907] CURRENT LITERATURE 229 



the climate. He directs attention especially to the water-storing tissue, which he 

 declares to be no xerophytic character (i. e., one that serves as an adaptation to a 



A • long dry period), but to have its relation to the transpiration of plants that have 



only to endure short dry periods. This tissue is almost confined to leaves of tropi- 



' cal and subtropical regions, where by the frequent rains and by the dews, which 



are heavy even in the dry periods, it can daily be refilled, quite independently of 

 the roots. This refilling Holtermann claims to have established experimentally; 

 but the report is not convincing, particularly as this process is alleged to take 



j place through the epidermis. If water can come in so, it can go out so; and the 



plant would be the gainer only when the period of evaporation was shorter than 

 the period of absorption. 



The third section discusses the leaf fall in the tropics. This, Holtermann 

 holds, is dependent on internal conditions which become active under the influence 

 of climatic factors. Leaves which fall off at the beginning of a dry period are not 

 built to withstand drought; and even if the fall be delayed by favorable conditions, 

 it is only delayed, abscission having become a hereditary peculiarity. 



The formation of growth zones is the fourth topic. The author undertakes 

 to show that the formation of zones in secondary wood is incited by climatic 



( 



I 



i 



I 



upo 



« * « « 



nally by direct adaptation, has become heritably fixed. J 



# factors act, he thinks, will always remain a problem. 



powers 



The last section, on direct adaptation, deals with water-storing tissue, gutter- 

 pointed and emarginate leaves, dwarfing, etc., as "caused" by definite external 

 conditions. Such new characters, called out at first by the release of laten: 

 Tnay become fixed and heritable, just as leaf fall and growth rings, or under other 

 conditions may again disappear. 



The book is full of interesting observations, which are unfortunately not easily 

 accessible for lack of an index. — C. R. B. 



Ecology of West Australia. — The series of monographs on plant geography^ 

 has received a notable addition in the se\^enth volume, dealing with the flora of 

 southwestern Australia, 3 by Dr. Diels. His thorough knowledge of the herbarium 

 material from this and similar regions, and his wide acquaintance with plant 

 distribution made him able to plan and execute in the most profitable way the 

 journey which he undertook in igoo-1902, in company with Dr. Peitzer, with the 

 support of the Humboldt fund of the Royal Prussian Academy of Sciences. 



The systematic results have already appeared, in collaboration with Peitzer, 

 I in Engler's Botanische Jahrbiicher. In this volume we have first, by way of 



^ Engler, a., und Drude, O., Die Vegetation dcr Erde. Sammlung pflanzen- 



'graphische 



896— 



3 DiELS, L., Die Pflanzenwelt von West Australien sudlich des Wendekreises 

 Imp. 8vo. pp. xii + 413. / map, figs. 82, pis. J4. Leipzig; Wilhclni Engelniann. 1906 

 ■*^ 36, geb. 37.50 (subs, price M 24, bound 25.50). 



K 



