360 WORTHINGTON G. SMITH, 
The Restinc-Sporsts of PERONOSPORA INFESTANS, Mont. 
By Worruineron G. Suitu, F.L.S. (With Plates XIX 
and XX.)! 
THE two accompanying photographs (Plate XIX) were 
taken from nature by the aid of the microscope on July 31st 
last. ‘They represent the oogonia and antheridia of Perono- 
spora infestans, Mont., from one of the tubers of the American 
potatoes grown this year in the garden of the Royal Horti- 
cultural Society at Chiswick. The whole plant experimented 
upon was badly attacked by the Peronospora, and on the 
tuber being cut intohalves the exposed surfaces became covered 
with the normal fruiting branches of the now well-known 
fungus. On these tubers being kept under glass for further 
experiment a condition of watery decomposition at once set 
in, and the tubers and water alike were infested in every 
direction by hyphz, oogonia and antheridia, similar to those 
here figured. I regret that I lost the greater part of the 
material from this individual tuber, as one half of the specimen 
suffered from too much moisture and the other half from too 
little; every one acquainted with moulds well knows that 
the least superabundance of moisture or the least drought 
at once destroys the mould. ‘The bodies here photographed 
were those present in the turbid fluid which oozed from the 
Peronospora-infected tuber, and the whole of this liquid I 
have preserved intact. For three or four days after the ex- 
udation had been placed in a phial these reproductive bodies 
floated, grew, and united in pairs on the surface; but after 
the lapse of a week they all descended to the bottom of the 
phial, where they have ever since remained. Before the 
phial was sealed repeated experiments were made with a 
test-tube, before many other observers, to show that the fecun- 
dated oospores were present in abundance at the bottom of 
the liquid. 
The photographs which accompany this paper are two of 
the best of a series of a dozen, and they were all taken 
1 The state of our knowledge of the life-history of Peronospora infestans, 
previously to Mr. Worthington G. Smith’s important observations, is sum- 
marized in the ‘ Quart. Journ. Micr. Sc.,’ 1874, pp. 176,177. Prof. De 
Bary’s recent investigations led him to the conclusion that the sexual state 
might occur on a separate plant. (‘ Nature,’ vol. x, p. 390.) This view has 
also been maintained by Mouillefert and by H. Jenkins (‘Journ. Roy. Agric. 
Soc.,’ 1874, p. 510). We understand, however, that Prof. De Bary has 
now abandoned it, and has recently obtained results entirely confirmatory 
of those of the author.—Eps, 
