PERONOSPORA INFESTANS. 183 



the opinion that these might ultimately be found to be the resting 

 spores of the Potato Peronospora. Last year Mr. Worthington 

 Smith detailed his examinations of diseased potato leaves from 

 Chiswick, in which he found spherical bodies precisely like those 

 described and figured by Montague, associated with, and, as he 

 believed, continuous with the mycelium of Peronospora. Other 

 bodies were found, having apparently the function of antheridia, 

 and these he saw applied to the surface of the globose bodies. 

 Under these circumstances Mr. Smith considered himself justified 

 in regarding the globose bodies not only as the Artotrogus of 

 Montague, but also as the resting spores of Peronospora. 



Subsequently Dr. de Bary investigated the same subject, at the 

 instigation of the Royal Agricultural Society, and published his 

 conclusions, that the mould (^Peronospora') possessed distinct 

 features as regards successive production of conidia so as to merit 

 distinction as a new genus under the name of Phytophthora. That 

 the globose bodies in question did not belong to this mould, but 

 were a species of Pythium, which he named Pythium vexans, and, 

 that the resting spores of the potato disease had not been dis- 

 covered. Here, then, he joined issue with Mr. Smith, and pro- 

 bably the succeeding controversy would not have brought us 

 nearer the truth had it not been associated with new and searching 

 examinations, which now promise to set the matter finally at rest. 

 We cannot enter upon the details of this discussion here, but we 

 may indicate how far the missing link is being supplied. The 

 '' resting spores " of Mr. Smith have been placed under favourable 

 conditions, and at once produced zoospores. This, however, was 

 insufficient evidence, for Pythium likewise developes zoospores 

 under similar conditions. Nevertheless, the experiments have been 

 carried further, the zoospores have germinated, and the mode of 

 growth, and branching of the threads, seem to be not those of a 

 Pytliiuni, but of a Peronospora. It may be that whilst these pages 

 are passing through the press the evidence has been completed by 

 the production of veritable conidia of Peronospora on the threads 

 developed from zoospores of the globose bodies called " resting 

 spores " by Mr. Smith. The presumption is now strongly in 

 favour of Mr. W. Smith's view being indisputably established, 

 and the controversy set at rest. 



CRYPTOGAMIC LITERATURE. 



CooKE, M. C. Two Coffee Diseases, in " Popular Science 

 Review," No. lix., March, 1876. 



Woodward, Dr. J. J. Note on the Markings of Navicula 

 rhomhoides, in « Monthly Microscopical Journal," May, 1876. 



BoTANiscHER Jahresbericht, Third Part for 1874. 



De Bary, A. Researches into the Nature of the Potato Fungus 

 {Peronospora inftstans), in " Journ. Bot.," April and May, 1876. 



