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PHYSIOLOGICAL STUDIES IN PLANT 
ANATOMY 
I. INTRODUCTION 
By J. H. PRIESTLEY 
I N the general title to this series of papers the phrase “Physio¬ 
logical Anatomy” has been avoided because of the significance 
it bears in Haberlandt’s great text-book, where a structure is re¬ 
garded as explained when it has been shown to be efficient for the 
performance of its physiological duties. The great series of data thus 
marshalled by Haberlandt appear to be rather anatomical con¬ 
tributions to the understanding of plant physiology than contribu¬ 
tions made by physiology to plant anatomy. 
It is true that, theoretically, Natural Selection may explain the 
existence of any useful working mechanism, but the mere demon¬ 
stration of usefulness tends to draw a veil over the way in which the 
mechanism comes into being, and any real explanation of the struc¬ 
ture must wait until its development has been traced and interpreted 
in terms of physico-chemical causation. Such developmental studies 
will require an extensive re-investigation of the problems of anatomy, 
undertaken largely from a physiological point of view, and it is in 
this sense that the following series of papers may be regarded as 
physiological studies in plant anatomy. 
The standpoint is not a new one; it has been expressed on several 
occasions by Lang(i), but so far as the writer is aware this is the first 
time it has been consistently applied to the detailed study of the 
development of a complex plant organism. From this standpoint, 
that of causal anatomy, a structure is not explained because it is 
adapted to its surroundings when mature, but as the inevitable out¬ 
come of the reaction between earlier developmental stages and its 
environment. Given these inter-related factors its development was 
inevitable, whether the mature structure is useful or not. That it is 
usually a useful and efficient structure remains, as before, an argu¬ 
ment for the effectiveness of Natural Selection. It is obvious that 
only a beginning can be made upon so vast a field and it is not claimed 
that the few results obtained from the study of a limited number of 
plants are necessarily of general application. The experience gained 
so far in this field of investigation makes it possible to define some 
of the general questions more clearly than would have been possible 
