THE POTATO TUBER. 
57 
An Investigation into the Structure and Functions 
of the Skin of the Potato Tuber. By F. Stoward, 
D.Sc. (Read April i6th, 1912.) 
Plates XIV. to XVII. 
PAGE. 
Introduction 57 
The Morphology of the Potato Tuber 59 
The Histology of the Potato Tuber 60 
The Comparative Impermeability of the Skin of the Tuber to 
Water and certain Salts and Acids in aqueous solution .... 69 
The Absorption of Water by Tubers 70 
The Steeping of Tubers in Brine and other Salt Solutions 70 
The Steeping of Tubers in solutions of Acids; the Imperme- 
ability of the Skin to Sulphuric Acid 73 
Summary 79 
Introduction. 
It is, perhaps, scarcely necessary to do more than 
simply indicate the economic importance of the potato-tuber. 
The fact that it serves as a human food-stuff, and that it 
represents the starting point of at least two industries of 
colossal magnitude — starch production and industrial alcohol 
—are sufficient to stamp it as a vegetable product of first 
importance. Nevertheless, that so common-place an object as 
an ordinary potato-tuber may serve as promising material 
for the purpose of a biological or physiological enquiry may 
at first sight appear to be doubtful. It may be contended 
that so well known a product must surely have been sub- 
jected to thorough investigation. The fact cannot be 
denied : the potato- tuber has undoubtedly been investigated 
from various standpoints — the biological, physiological, 
chemical, and, during recent years, pathological standpoints ; 
but the general result of these investigations has been to 
stimulate further enquiry, and to develop new lines of 
research. One of the invariable results of scientific investi- 
gation, using the phrase in its proper meaning, is to open 
up new avenues of research. 
However complete an investigator’s work and its 
attendant results may have been in any particular field 
of enquiry, there still remain areas which have not been 
covered. 
The cultivated tuber, in common with other plants, 
is subject to attack from various natural parasites. These 
may be of fungoid, bacterial or animal origin. Among the 
aims of the young science of plant pathology is the study 
of these disease producing organisms, with special reference 
to their life histories, modes of attack, and the nature of 
the pathological changes induced by them in the plant 
attacked. Such studies, when directed to economic ends, 
lead to attempts to devise and develop means calculated to 
