188 SECTIONAL ADDRESSES 
due to insufficiency of available sulphur in the soil; it can be speedily 
remedied by the application of sulphur or salts containing sulphur. 
Several of the functional diseases of apples in storage, some of which are 
caused by respiratory disturbances, have been investigated by plant 
physiologists at the Low Temperature Research Station, Cambridge, and 
by pathologists in the United States and Australia. I will refer briefly to 
one of these troubles. For many years large losses had been incurred in 
the importation of apples from the Antipodes into this country, owing to 
the disease known as ‘ brown heart,’ which is characterised by a brown 
discoloration of the flesh between the skin and the core. Kidd and 
West 78 shewed that this condition was brought about by disturbances in 
the respiration of the cells of the apple owing to the accumulation of a 
high percentage of carbon dioxide in the atmosphere surrounding the 
fruit in the holds of the ships. Nowadays greater care is taken than 
formerly to ensure adequate ventilation in the holds of ships carrying 
cargoes of apples, with the result that ‘ brown heart ’ has been practically 
eliminated. Another kind of plant injury that is receiving renewed 
attention is that caused by frost. In this connection I have time ony to 
refer to the damage sustained by the larch tree in Britain by late spring 
and early autumn frosts. Day and Peace 7 claim, I think justifiably, 
that much of the canker or blister disease of the larch tree, generally 
believed to be due to a species of Dasyscypha, is primarily caused by 
such frosts, which kill groups of active cambium cells. There is still 
an enormous field for research on the functional disorders of plants not 
caused by parasitic organisms, and it is particularly in this branch of the 
study of disease in plants that the help of the physiologist is required. 
Plant pathology is a subject with wide ramifications and many-sided 
interests. It is an important connecting link between botany and crop 
husbandry, and the economic importance of the study of plant diseases is 
self-evident. From the academic standpoint research in plant pathology 
is becoming more and more closely associated with physiology, and it is 
clear that future advances in the understanding of disease in plants will 
become more and more dependent upon the use of analytical methods 
similar to those employed by the physiologist. In this address I have tried 
to shew that plant pathology has a contribution to make to our knowledge 
of botany in general and that many pathological investigations are of 
interest to the pure botanist. Furthermore, just as researches in medical 
science have added greatly to our comprehension of the attributes of 
protoplasm so does plant pathology provide an instrument for increasing 
our knowledge of general biological principles. 
78 Dept. Sci. and Indust. Res., Food Investig. Bd., Spec. Rep. No. 12, 1923. 
79 Oxford Fovestvy Memoirs, No. 16, 1934. 
