252 APPEKDIX. [No. XV.c. 



No. XV.c. 

 RECENT RESEARCHES ON THE POTATO DISEASE.— Royal 



HOETICULTITEAI, SOOIETT, SoiENTII'IC COMMITTEE, April Stll, 1876. 



Maxwell T. Masters, M.D., F.R.S., in the chair. 



Mb. "W. G. Smith exhibited a number of new di-awings and referred to 

 a recent examination made by bim of 360 slides prepared by Mr. Alfred 

 Smee in the first year of the potato murrain, 1845. These slides included 

 slices of diseased potato stems, tubers and leaves, and aphides taken from 

 infected plants. In these tubers and stems, and also within and upon 

 the bodies of the aphides, Mr. Smith had found a large number of the 

 bodies recently referred by him to the secondary condition of the potato 

 fungas. 



" During the last fortnight," continued Mr. Smith, " Mr. Alfred Smee 

 has placed in my hands for microscopic examination no fewer than 360 

 slides having reference to the potato disease. These slides were all pre- 

 pared by Mr. Smee in the first year of the great potato murrain, viz. 

 1845, and the preparations include potato leaves, slices of stem and tuber, 

 and aphides taken from diseased potato plants in that year. 



" Out of 104 slides illustrative of the structure of the potato plant, 

 twenty-seven distinctly show the oogonia and antheridia, as illustrated by 

 me in the ' Gardeners' Chronicle :' these bodies mostly occur in. the stems 

 and tubers of the 1845 potatoes, just where they principally occurred in 

 the Chiswick potatoes last year. 



" Of the remaining slides of insects, principally aphides, about one- 

 half show traces of the same bodies. The threads are growing both inside 

 and outside the aphides : sometimes the oogonia are deeply buried in the 

 body, whilst the whole insect is traversed by mycelial threads ; many of the 

 oogonia are inside the legs, sometimes inside the feelers. These oogonia 

 and antheridia are presumedly the same as those I found last year upon 

 and within the diseased Chiswick potatoes, and they are exactly the same 

 as the bodies now to be seen in Mr. Smee's 1845 potato preparations. 



" On two special slides of aphides the insects are densely covered 

 externally with a fungus in fruit. So dense is the covering, that very 

 little of the insect's body can be seen. This fruit is almost identical in 

 size and form with the fruit of Peronospora infestans, and, like the latter, 

 it shows a marked differentiation of its contents, and apparently produces 

 zoospores. By carefully searching amongst this dense mass of fruit, the 

 oogonia and antheridia above mentioned can also be detected. 



" Without wishing to speculate on the meaning of these new facts, 

 it must be confessed that this new association of these fungoid bodies on 

 diseased potatoes and aphides is new and suggestive. As my last year's 

 Chiswick resting-spores are apparently stiU aUve, though latent, I hope 

 to try some expeiiments with them as soon as they start into life in the 

 early summer." 



Mr. Renny considered that the relationship to Pythium was 

 strengthened by Mr. Smee's preparations. In Saprolegnia the antherid 

 was always borne on finer threads than the oogonium. — From the 'Gardeners^ 

 Chronicle,' April 8th, 1876. 



