244 D. T. MACDOUGAL 



chanical penetration of the host, as it would be far greater than 

 any force attributable to osmotic action. 



After the haustorial development has carried that organ to a 

 mature stage the nutritive contact with the host is one in which 

 osmosis doubtless plays an important part. The proportion of 

 nitrogenous substance in the parasite, the acidity, and the con- 

 centration of salts might be the determining factors m both 

 the making and maintenance of a nutritive couple of host and 

 parasite. 



