192 PHYTOPHTHORA PARASITICA. 



hyphse at the point of origin (Plate V, Fig. 4e). They are generally 

 curved, either concave or convex ; they are more or less thickened 

 either on one or both sides by the deposition of cellulose on them. 

 The thickening is either elliptical or conical (Plate V, Fig. 4). It 

 resembles callose caps on sieve plates. The cellulose thickening 

 when stained with Schulze's solution does not take a homogenous 

 blue or violet colour but different shades of blue or violet. This 

 shows that the cellulose on the septa has been deposited in layers. 

 On rare occasions branches have been found to grow through septa 

 (Plate V, Fig. 6). Cellulose ingrowths have been found to form 

 false septa in hyphse (Plate V, Fig. 5). They differ from the ordinary 

 septa in not having their characteristic curve, in being broadened 

 at the ends and not in the middle, and in not being laid down in 

 plates, but in being ingrowths from the inner layer of the hypha 

 walls. The false septa are formed either by two cellulose pegs 

 growing in from the opposite walls and meeting at some point 

 (Plate V, Figs. 4d and 5c) or by cap-like depositions of cellulose on 

 the ingrowths (Plate V, Fig. 5b). 



The sporangia are borne on simple stalks, but in water cultures 

 and in certain media the stalks are as irregularly branched as those 

 of Ph. omnivora and of Ph. omnivora, var. Arecce. The sporangia 

 are generally apical as in a typical Phytophihora ; but they are often 

 intercalar and sometimes lateral as well ; the end of a hypha swells 

 as if it was forming a sporangium, but for some unknown cause the 

 swelling does not increase and produces three or four short lateral 

 branches, each of which terminates in a sporangium. Occasionally 

 an apical branch also arises from the swelling, which prolongs the 

 vegetative growth of the original hypha. The sporangia are generally 

 pear-shaped but intercalar sporangia are usually round (Plate V, Fig. 

 lb) ; they do not vary much in shape but they vary a great deal in size. 

 The variation is between 11-60 x 10-45m, on an average 25-50 x 

 20-40/*, and consequently the number of zoospores in them is very 

 irregular. They have from 5 to 45 zoospores, on an average 30. 

 Sporangia and zoospores from diseased leaves are found to be smaller 

 man those from pure cultures. Sporangia have usually one papilla 



