II SCIENCE PROGRESS. 



and so on. The obvious objection, that the author does not help us in 

 really knowing why one organism develops in this way and another in 

 that way, is unfortunately one which we are not in a position at present 

 to remove. In this connection Hertwig stands in sharp contrast with 

 Weismann. The latter has formulated a theory of heredity which was 

 intended to enable us to understand the why and wherefore of all kinds 

 and all grades of organisation. Hertwig, on the other hand, starts 

 with the ovum which is already endowed with the potentialities of the 

 species, and he is content to trace the influence of the various causes 

 which may effect or modify the course of its development to the adult 

 organism, without saying wherein the inherent forces exist which 

 primarily determine the ultimate form. But he has at least pointed 

 out most forcibly the difficulties in the way of accepting any of the 

 explanations as yet suggested. 



Lehrhnch der Oekologischen Pflanzciigcographie, Eine Einfuhrimgiyi die 

 Kenntnis der Pjlanzenvcreinc. Von Dr. Eugen Warming. 

 Deutsche ausgabe von Dr. Emil Knoblauch. Berlin: Gebriider 

 Borntraeger, 1896. 



It has often been a subject of lamentation, in this country at any 

 rate, that Naturalists are not so common amongst Biologists as they 

 used to be. This is no doubt true, and it is clearly reflected in the 

 modern type of text-book, whether Zoological or Botanical. As regards 

 the latter science, the causes are to be sought partly in the comparative 

 neglect into which the study of Systematic Botany has fallen. The 

 centre of gravity has shifted, and an intimate knowledge of the minute 

 structure, rather than of the external forms, of plants has become per- 

 haps a little too clamorously demanded. 



But signs are not lacking to indicate that the pendulum has begun 

 to swing back again. Many of the younger botanists have already 

 begun to perceive that study of plants as they grow is just as indis- 

 pensable as is a knowledge of the structure of their vascular bundles or 

 of their apical meristems. And on this perception it is to be hoped 

 performance will follow. No doubt some of the disinclination to 

 devote much attention to the systematic branch of the science has been 

 partly due to a sort of feeling that taxonomy is rather " played out". 

 We do not, however, by any means concede this ; and certain it is that 

 no student who desires to be in touch with the problems of the 

 immediate future can afford to dispense with the range of knowledge 

 which a moderate acquaintance with taxonomy alone can give. 



One of the questions which in its details is gradually shaping 

 itself more and more clearly is the important one which concerns 

 adaptation to the environment. We know well enough that certain 

 districts are associated with certain types of vegetation ; we want 

 further to know what it is which determines the peculiar features of 

 these dissimilar floras. But the more closely we examine the problem 



