Dey— Studies in the Physiology of Parasitism. V. 31 1 
From the surface of the appressorium in contact with the host, a peg- 
like £ infection hypha * grows out, which ruptures mechanically the cuticular 
layer, and then brings about swelling of the subcuticular layers, no doubt 
by enzymic action. 
There is no evidence that the ‘infection hypha’ can exert any swelling, 
disorganizing, or other chemical action upon the cuticle. 
The mechanism by which the ‘ infection hypha ’ of C. Lindemuthianum 
penetrates the host surface is thus in all respects similar to the mechanism 
employed by the germ-tube of Botrytis cinerea . 
References. 
1. Blackman, V. H., and Welsford, E. J. : Studies in the Physiology of Parasitism. II. Infection 
by Botrytis cinerea. Ann. Bot., vol. xxx, p. 389, 1916. 
2. Brown, W. : Studies in the Physiology of Parasitism. I. The Action of Botrytis cinerea. Ann. 
Bot., vol. xxix, p. 313, 1915. 
3. : Studies in the Physiology of Parasitism. III. On the Relation between the 
‘ Infection Drop’ and the Underlying Host Tissue. Ann. Bot., vol. xxx, p. 439, 1916. 
4. Busgen, M. : Ueber einige Eigenschaften der Keimlinge parasitischer Pilze. Bot. Zeit., vol. i, 
P- 53, 1893. 
5. Edgerton, C. W. : Effect of Temperature on Glomerella. Phytopath., vol. v, p. 247, 1915. 
6. Frank, B. : Ueber einige neue, weniger bekannte Pflanzenlcrankheiten. Land. Jahrb., vol. xii, 
p. 511,1883.. 
7. Hasselbring, H. : The Appressoria of the Anthracnoses. Bot. Gaz., vol. xlii, p. 135, 1906. 
8. Muncie, J. H. : Experiments on the Control of Bean Blight. Michigan Agri. Coll. Expt. Sta. 
Technical Bull., 38, 1917. 
9. Stoneman, B. : A Comparative Study of the Development of some Anthracnoses. Bot. Gaz., 
vol. xxvi, p. 69, 1898. 
10. Strasburger und Koernicke : Botanisches Praktikum, 5th ed., p. 809, 1913. 
11. Voges, E. : Die Bekampfung des Fusicladium. Zeit. f. Pflanzenkrank., vol. xx, p. 385, 1910. 
12. Ward, H. M. : A Lily Disease. Ann. Bot., vol. ii, p. 319, 1888. 
13. : On the Histology of Uredo dispersa , Erikss., and the ‘ Mycoplasm ’ Hypothesis. 
Phil. Trans., B., vol. cxcvi, p. 26. 
14. Whetzel, H. PI. : Some Diseases of Beans. Cornell Univ. Agri. Expt. Sta. Bull., 239, 1906. 
15; - — : Bean Anthracnose. Ibid., 255, 1908. 
EXPLANATION OF FIGURES IN PLATE XXI. 
Illustrating Mr. Dey’s paper on Physiology of Parasitism. 
All figures except 1-4 a were drawn with the camera lucida, under Koristka in semi-apochro- ' 
matic, oil-immersion objective, and No. 8 eyepiece. Figs. 1-4 A were drawn under Leitz j 1 ^ in. oil- 
immersion objective, and No. 4 eyepiece. 
The host tissue figured is that of the pod of Phaseolus vulgaris. 
Fig. 1. Germinating spore, x 1050. 
Figs. 2-3 a. Germinating spore, showing the appressorium : drawn from material fixed in 
picro-nigrosin after twenty-four hours of growth, x 1050, 
