Waterhouse. — Studies in the Physiology of Parasitism. VII. 563 
cuticle. A parallel series of infections with Puccinia Malvacearum , Mont., 
was made on leaves of hollyhock, in which stomata are present on the 
upper surface of the leaf. Eriksson (6, p. 75) states that in no case was he 
able to observe the entry of a germ tube through a stoma. In one case 
the beak-like projection of a germinating sporidium was found inserted into 
a stomatal pore, although, in agreement with Eriksson, the mode of entry 
was by a penetration of the cuticle in all other cases. 
After penetrating the epidermal wall, the tip of the infection hypha at 
once begins to swell (Fig. 16). The swelling enlarges and becomes an 
elongated vesicle (Fig. 17), which branches (Fig. 19) and gives rise to the 
uninucleate mycelium which invades the host tissue. 
In conclusion, the author wishes to express to Professor V. H. Blackman 
his gratitude for helpful advice and criticism ; also to Dr. S. G. Paine, and 
Mr. J. F. Dastur, of India, for help in connexion with the work. 
Summary. 
The infection of Berberis vulgaris by the sporidia of Puccinia graminis 
has been studied. 
In the germinating sporidia, a mucilaginous investment of the germ 
tube can be shown to be present. 
Penetration of the cuticle is brought about by means of a very fine 
style-like infection hypha, which may be put out either from the end 
of a definite germ tube or from a short beak-like outgrowth of the 
sporidium. 
There is no evidence of any chemical action upon the cuticle. The 
puncture of the cuticle appears to be brought about solely by the mechanical 
pressure exerted by the infection hypha as it develops from the germinating 
sporidium or germ tube. The sporidial beak or germ tube from which the 
infecting style grows is firmly fixed to the leaf surface by means of a 
mucilaginous investment. 
As soon as the infection style has penetrated through the epidermal 
wall it sw T ells into a vesicle from which the mycelium arises. 
The entry of the parasite causes at first no visible alteration of the cell 
contents of the host plant. 
References. 
1. Blackman, V. H., and Welsford, E. J. (1916) : Studies in the Physiology of Parasitism. II. 
Infection by Botrytis cinerea. Ann. Bot., xxx. 389. 
2. Dey, P. K. (1919) : Studies in the Physiology of Parasitism. V. Infection by Colletotrichum 
lindemuthianum. Ibid., xxxiii. 305. 
3. Evans, I. B. Pole (1907) : The Cereal Rusts. I. Development of their Uredo mycelia. Ibid., 
xxi. 441. 
