BUTLER AND KULKARNI. 245 



than the aerial hyphae (PL III, Fig. 1). The hyphce which penetrate 

 the medium are still more branched and are much less regular in 

 diameter than the superficial mycelium (PI. Ill, Fig. 2). Their 

 ultimate ramifications are much branched, irregularly swollen, for 

 the most part densely filled with protoplasm and sparingly septate 

 (PI. Ill, Fig. 3). 



The sporangia are borne both laterally and terminally on the 

 aerial hyphne (PI. Ill, Fig. 4). As in those found naturally on the 

 leaf, their stalks are as a rule much narrowed and they break off, 

 with a portion of the stalk attached, very readily. Sometimes, 

 however, especially in secondary sporangia formed by the germin- 

 ation of primary sporangia, the stalk differs little from an ordin- 

 ary hypha (Fig. la). Occasionally the insertion is by a broad 

 base or the sporangium may develop as a unilateral swelling in the 

 course of a hypha (Fig. lb, Fig. 6, upper sporangium). Fig. 5 

 shows a group of sporangia from a French-bean agar culture 20 

 days old. They are still less uniform in size and shape than those 

 found on the leaf, measuring from 20 to 61 by 15 to 31 /* in diameter 

 and varying from almost cylindrical to broadly oval or club-shaped. 

 They are, however, more elongated on the whole than in any other 

 species of Phytophthora hitherto recorded. The papilla is always 

 short and blunt and the base is marked at the point of insertion on 

 the stalk by a strong cellulose plug projecting into the sporangium. 

 Many of the sporangia developed in culture, fall off within the 

 tube, and in the absence of sufficient moisture to allow of zoospore 

 production, most of these germinate as conidia by putting out one 

 or more germ-tubes. In older cultures, a considerable proportion 

 of the growth consists of hyphae which have arisen from the first 

 formed spores. This secondary growth again bears sporangia 

 and it is at least conceivable that under certain conditions there 

 may be a continuous succession of the vegetative and asexually 

 reproductive stages of the fungus in cultivated soils, not only in 

 this species, but in Phytophthora infestans and other species whose 

 persistence from year to year, without any form of resting-spore, 

 having been discovered under natural conditions, is still difficult 



