256 K. J. nrTLETi. 



in diameter, tlie wall ])eing up to 4 /^ thick. Trreoular sha])es are 

 sometimes met with (phite V, figs. 8 and 9). 



The stalk hypha is sometimes exactly like those of the vegeta- 

 tive mycelium, sometimes variously dilated and irregularly branch- 

 ed (plate V, figs. 2 to 5). In many cases it is septate some dis- 

 tance below the spore, the appearance resembling the hypogynal 

 antheridia found in P. de Baryanum, P. Artotrogus and other mem- 

 bers of the genus (plate V, figs. 1, 2 and 5). In other cases branches 

 from the stalk hyphse or from neighbouring ones closely encircled 

 the spore (plate V, figs. 2 and 4), and it was these appearances, as 

 well as the general resemblance to an oospore, which led to its being 

 described previously as a sexual spore. However, many cases have 

 since been seen in which it was formed terminally on a simple un- 

 septate stalk entirely free from adjacent hyphse and with no trace 

 of anything that could be construed as an antheridium (plate V, 

 fig. 6). This, together with the absence of any differentiation of the 

 contents into an oospore lying within an oogonium, quite precludes 

 its being construed as a sexual formation, and it must be considered 

 as a much more highly developed equivalent of the resting conidia 

 of P. de Baryanum. The germination has been previously described 

 and is invariably by a germ-tube, which may branch and always 

 bears terminal sporangia after a short growth (plate V, fig. 10). 

 The period during which these spores preserve their vitality is not 

 known, but is likely to be at least some months. 



No trace of true oospores has been discovered during the period 

 that the parasite has been under observation. A sufficient number 

 of cases has been examined to make it probable that if they occur 

 they must be rare and are not likely to be of any practical importance 

 in the life of the species. 



From the observations made at different times of the year it has 

 been noticed that sporangia are usually found on the attacked leaves 

 only at the periods of considerable rainfall or heavy dews. They 

 were found in June, July and August without much difficulty, less 

 often in September. In March none could be found in one locality 

 where a rather thorough search was made. Besting conidia are less 



