514 H. MARSHALL WARD. 



was struggling under unfavourable circumstances must not be 

 forgotten — since we have seen that it apparently became 

 driven out of the field eventually by its successful rival, P. 

 gracile^ De Bary — and such circumstances may have affected 

 the normal course of its development, even in details. Never- 

 theless, there was no direct evidence to show that such was the 

 case in the specimens figured. 



Another peculiarity which renders the separation of this 

 Pythium necessary was the behaviour of the sub-sporangial 

 portion of the hypha. As shown in fig. 44, the end of the 

 hypha grows through the empty sporangium, and becomes 

 continued as a long hypha which can certainly bear a zoo- 

 sporangium again at its apex, though I only once saw one 

 such, and that not fully developed. 



All things considered, it seems necessary to regard the above 

 form as distinct from any yet described in this paper. Whe- 

 ther it is the form called P. ferax by De Bary^ cannot be 

 decided until the oospores, &c. are observed, though it 

 appears so far to answer to the descriptions given of that 

 species. 



The last representative of this remarkable genus which I 

 have actually studied, is P. intermedium, De Bary,^ a form 

 which occurs mingled with P. De Baryanum both on dead 

 and living plants. My specimens were obtained through the 

 kindness of Prof. De Bary, and cultivated on killed cress- 

 seedlings as before. The sexual organs have never been 

 observed, and its only claim to be regarded as a distinct species 

 seems to be its habit of producing the conidia in vertical 

 series (figs. 45, 46), and the many similarities between these 

 conidia and those of the Peronosporeae ; facts of which 

 advantage has been taken in comparing the two groups.^ The 

 chief points are as follows, according to De Bary : the conidia 



• 'Bot. Zeit.,' 1881, p. 562. I have only once seen the zoosporangia 

 of P. ferax, through the kindness of Prof. De Bary, and cannot decide 

 that the two forms are identical. 



2 'Bot. Zeit..' 1881, p. 553. 



» ' Bot. Zeitung,' 1881, loo. cit. 



