49i H. MARSHALL WARD. 



(Hum at 12.30 being very small (fig. 10, k). The oosphere, 

 during the last-named stages, slowly came to the centre of the 

 oogonium (fig. 10, k), and then ceased to revolve. Mean- 

 while a very delicate skin had been formed over the now 

 smooth exterior of the oosphere. This was first detected 

 about 11. oO (fig. 10, «/), but had become much more evident 

 at 12.30 (fig. iO, k). At 3 o'clock p.m. the antheridium 

 contained practically nothing except a trace of granular matter; 

 all its remaining protoplasm had passed over into the 

 oosphere, thus changing it into an oospore. At this hour, 

 too, the oospore — as it must now be termed — had become 

 clothed with a thick envelope. The process of fertilisation was 

 completed, and the oospore was "ripe" (fig. 10, /). A com- 

 ])arison of figs. Jc and / shows that the protoplasm which 

 ])ersisted between the oosphere and the oogonium wall at 

 l!2.30 had entirely disappeared at 3 o'clock. There can be no 

 doubt that it became used up to form the thick envelope formed 

 in the interval around the oospore. Long after the completion 

 of the latter, the empty antheridium and tube can still be re- 

 cognised, though the ripe oospore lies loosely in the oogonium. 

 In such condition the oospores remain testing for months, as 

 can be seen in old material (figs. 6 and 7). 



It was already known, from the researches of Hesse, that P. 

 De Baryanum attacks many different kinds of living and 

 dead plants, and it seems certain that the mycelium and 

 spores of this fungus are very wide spread in European soils. 

 Although this fungus is so omnivorous, however, there are 

 some plants vVhich it apparently refuses to attack, e. g. fresh 

 water Algse. Hesse observed it on Trifoliura, Spergula, 

 Panicum, and Zea, besides cultivating it on Camelina and 

 Lepidium seedlings; on the other hand, he found that nume- 

 rous allied plants — among others Brassica, Fisum, Hor- 

 deum — refused to be infected by P. De Baryanum. Hesse 

 also failed to cultivate it on Potato seedlings. 



The tuber of this latter plant, however, is in reality a very 

 good medium for the cultivation of the fungus, and my 

 researches go to show that Hesse's list of favorable host 



