58 
F. STOWARD, D.SC. 
prevent or suppress certain plant diseases. The success 
or non-success of these means depends in great measure on 
the extent to which scientific enquiry has been able ac- 
curately to elucidate the actual nature of the causation of 
diseases in plants. 
During recent years a considerable amount of investi- 
gative work has been devoted to the study of the destructive 
action of various powerful poisons on parasitic organsims. 
The treatment of tubers affected with tire fungous disease 
known as “ scab ” furnishes a concrete example of this 
mode of treatment. “ Scab ” infected tubers are steeped in 
aqueous solutions of formalin or corrosive sublimate, with 
the object of destroying the infecting fungus. The duration 
of immersion being so selected as to not seriously impair 
or endanger the vitality of the buds of the treated tubers. 
Obviously the question presents itself whether absorption 
of these poisonous substances occurs under the conditions 
of treatment selected. If absorption of the poison is 
postulated the further question presents itself whether 
absorption takes place through both buds and skin, or 
buds alone. Careful search through the literature at my 
disposal has so far failed to throw any light on this question, 
which would lead me to consider that it has hitherto been 
made the subject of any special enquiry. It will be evident 
whether or not the poisonous substances mentioned, or other 
soluble chemical substances, permeate the skin of the steeped 
tuber, turns largely on the structure and properties of the 
skin itself, and in particular on its behaviour towards 
chemical substances in solution ; in other words, the de- 
velopment of the subject obviously rests mainly on the 
manner in which the skin functions in regard to its per- 
meation by these substances. 
The present paper accordingly comprises a short 
account of the skin of the tuber, with special reference to 
certain of its functions and properties. 
Briefly stated, the main divisions of the subject include : 
(1) The morphology (external form and character- 
istics) and histology (minute anatomy) of the 
tuber, with special reference to the skin and 
its protective function. 
(2) Some of the more obvious effects attendant on 
experimental mutilation of tubers as evidenced 
by sectioning, removal of the skin, or excision 
of the “ eyes.” 
(3) The retard ative influence on the loss of weight 
by tubers as a result of the treatment of 
“ cut sets ” with certain chemical substances, 
and the subsequent influence on plant growth 
exercised by such treatment. 
