BUTLER AND KULKARNI. 251 



water gave in some cases visible signs of infection within six hours. 

 Few parasites are known which produce such rapid results as this. 

 In twenty-four hours brown spots at the point of inoculation were 

 well developed. On the second day the patches were larger and 

 yellow drops of liquid were oozing out on their surface. On the 

 third day sporangia were formed. Controls kept under similar 

 conditions showed no sign of disease. The germ- tubes from sporan- 

 gia which germinate direct as conidia were also found capable of 

 penetrating the leaf, entering across or between the lower epidermal 

 cells. 



Infection from zoospores takes place as shown in Plate II, 

 Figs. 2 and 3, which were taken 24 hours after inoculation. The 

 germ-tube pierces the cuticle, frequently swelling up or running 

 for a short distance in the thickness of the outer covering of the 

 epidermis (Fig. 2). It then either enters the epidermal cell or 

 passes down in the partition wall between two cells. In the meso- 

 phyll it pursues a strictly intercellular course, sending haustoria 

 into the neighbouring cells. When fructification is about to com- 

 mence hyphae from the intercellular mycelium of the mesophyll 

 again penetrate the epidermal cells to reach the surface (Figs. 1 

 and 4). They may also, as shown in Fig. 1, emerge through stomata 

 or at the junction between adjoining cells. 



Inoculations were next undertaken on a number of plants 

 known to be attacked by previously described species of Phytoph- 

 tliora. Excepting Colocasia none of the Aracece appear to serve 

 as hosts for the genus, several species of which, however, have a 

 wide range of hosts. 



The following table gives the details of these inoculations, all 

 of which were made from pure cultures by sowing some of the spor- 

 angium-bearing mycelium in distilled water and using the suspen- 

 sion for the inoculations as soon as the water contained plenty of 

 swimming zoospores. The plants were grown in pots and the 

 inoculations done by placing a drop of the suspension on the un- 

 wounded or wounded leaf or stem of the plant and covering with a 

 bell jar. The drops generally persisted for at least 48 hours, which 



