Communications. 279 



under a bell glass, and there has been no ofTensive odor and to no 

 appreciable extent has there been any mould, infusoria or para- 

 sites except Peronospora hifestans itself, and the other which is 

 equally destructive to potatoes, known under the name of Fusi- 

 sjporium Solani. In investigating the potato disease it was almost 

 as important to discover the entire life history of the Fusisporium 

 as of the Peronospora, and fortunately the materials preserved 

 gave a perfect clue to the entire life history of both. Mr. 

 Broome's material has in the same manner been free from an 

 excessive number of other fungi and infusoria. 



The germination of the resting spores was awaited with the 

 greatest anxiety ; and, as I never knew from one day to another 

 whether or not these bodies might all collapse and perish, I was 

 under the necessity of dividing the material and keeping a constant 

 lookout for results under different conditions. With this object 

 in view, therefore, I kept some of the bodies moist in pure water, 

 others in diluted expressed juice of horse-dung, others in expressed 

 juice of fresh potato leaves, others upon extremely thin slices of 

 potato or on crushed potato mash, others in saccharine fluid, others 

 in nitrogen gas, some between pieces of glass kept constantly 

 moist, some upon broken tile (also kept constantly moist), and 

 some upon potato leaves as they grew upon the living plant. 

 Besides this, I have had a quarter of a hundred of slices, kept damp 

 and under examination every day (almost night and day) for the 

 last three months. All these preparations I have kept constantly 

 and uniformly moist under darkened bell-glasses, as darkness in- 

 variably assists the growth of spores of all kinds. 



The first new fact worthy of note is this : many of the resting 

 spores grew in size during nine months of their rest to twice their 

 original diameter, or about four times their original bulk, and their 

 aspect gradually changed from almost smooth, semi-transparent 

 bladders, to brown, more or less rough and warted or cchinulate 

 spheres. These latter brown, mature bodies were quite the same 

 in character with those so sparingly seen last June and July. 

 How they arose last year no one saw, but probably the wet 

 "weather of the early summer caused their appearance. It does 

 not follow, because the resting spores have taken a year to artifi- 



