300 DISEASES OF FIELD & GARDEN CROPS. [OH. 



been seen for many years. We were, therefore, naturally 

 desirous of making a close examination of them. Some 

 of the earliest examples were sent on to us, and as we 

 were well acquainted with the potato fungus and its habit 

 of growth, we placed a series of infected leaves one over 

 the other, like the leaves of a book in a saucer. To keep 

 the leaves constantly and naturally moist, we placed a 

 very little water in the saucer, and this water just touched 

 the points of the leaves. The saucer was next slightly 

 tilted, so that the water might remain at one spot, and 

 the leaves slowly and naturally absorb it. The saucer 

 with the leaves was then placed under a bell-glass, the 

 bell-glass was covered with a cloth, and the whole kept in 

 a warm room. The potato leaves were then, as we thought, 

 in a favourable position for the full development of the 

 Peronospora, with no chance of a sudden check from too 

 much dryness or cold. At that time we had no idea 

 whatever in the direction of the artificial production of 

 oospores or resting -spores ; but on examining the potato 

 leaves as they gradually fell into decay, we were surprised 

 to see numerous examples of what we believed to be 

 Artotrogus attached to the Peronospora mycelium. At 

 first the examples were few in number, but at length they 

 were abundant. Soon after our results were published, 

 Mr. C. Edmund Broome, M.A., F.L.S., of Batheaston, 

 repeated the experiments, and obtained results precisely 

 the same with ours. Ultimately Mr. Broome went over 

 the ground a second time, and again obtained like results ; 

 at length, many other observers repeated the experiments, 

 and always with the same issue. 



A very successful plan for procuring resting -spores, 

 and one which we have not known to fail, was last year 

 suggested to us by our friend Mr. A. Stephen Wilson. A 

 number of leaves must be taken from potato plants invaded 

 by Peronospora infestans, Mont.; these leaves must be 

 slightly moistened and placed one over the other near the 

 top, inside a bell-glass ; the bell-glass must then be put 



