Studies in the Physiology of Parasitism. 1 
IV. On the Distribution of Cytase in Cultures of Botrytis 
cinerea. 
BY 
WILLIAM BROWN, M.A., D.Sc., 
From the Department of Plant Physiology and Pathology , Imperial College of Science and 
Technology , London. 
I N the first of these studies a method was described by which a powerful 
enzymic solution could be obtained in reasonable quantities from 
fungal germ tubes of one day’s age. It was claimed on a priori grounds 
that such an extract was more suitable for the study of the question 
of the nature of the active principle responsible for the breaking down of 
the host tissue in advance of the growth of the hyphae than the extracts 
which had been employed by previous investigators. The present paper 
relates to an investigation carried out with the object of determining in 
what way enzymic preparations obtained from the same strain of fungus may 
differ from each other. Though of a purely enzymological interest, these 
results have been incorporated in the present series, partly on account of 
the light which they throw on the nature of the extracts employed by 
previous investigators, and partly because of their bearing on the manner 
in which fungi secrete enzymes and on the technique of extraction. 
It will add to clearness to tabulate first of all the factors which have 
been found to influence markedly the activity of the enzymic preparation 
obtainable from a fungal culture. These are : 
i. The density of sowing of the spores. 
2. The length of the period allowed for development. 
3. The nature of the nutrient employed. 
It must be emphasized at this point, in order to prevent misconception, 
that the first factor mentioned is not a factor per se. It will appear in the 
sequel that the essential factor concerned in the obtaining of a strong 
extract is the proportion of actively growing mycelium to that which has 
already ceased to grow. Variation of the density of spore-sowing, together 
1 For No. I of this series, see Ann. Bot., vol. xxix, 1915, p. 313; for No. II, see Ann. Bot., 
vol. xxx, 1916, p. 389; for No. Ill, see Ann. Bot., vol. xxx, 1916, p. 399. 
[Annals of Botany, Vol. XXXI. Nos. CXXIII and CXXIV. July and October, 1917.] 
