No. XV.c.] APPENDIX. 253 



In 1875 it thus appears that Mr. Worthington Smith discovered the 

 secondary form of fruit of the potato fungus in the seed tubers of imported 

 American potatoes growing at Chiswick ; and for this discovery the Royal 

 Horticultural Society bestowed upon him their Knightian gold medal. 

 Until that year it would appear that these secondary forms of fruit of 

 the fungus were unknown, although their existence had been previously 

 suspected. 



No one challenged Mr. Smith's interpretation of the bodies discovered 

 except Professor De Barry, the French botanist. Professor De Barry 

 stated that he had seen somewhat similar bodies at times within potato 

 plants, but he considered they could not belong to the potato fungus, 

 because he could not make them complete their (fungus) entire life within 

 the potato plant, although he could make them apparently complete it in 

 the decaying bodies of minute insects. This opinion of Professor De Barry 

 was invalidated by some contemporaneous observations made by Dr. 

 Sadebeck, of Berlin, who said he had seen a parasite similar to that of 

 Mr. Smith's and Professor De Barry's growing on a potato plant at 

 Coblentz, and producing a disease in no way to be distinguished from the 

 ordinary murrain of potatoes. The question then presented itself whether 

 the potato fungus could grow on animal substances, like some of the fungi 

 to which it was immediately allied, as the fungus of house-flies, of silk- 

 worms, &c. 



As it was the winter season, 1876, when this question arose, Mr. Smith 

 applied to Mr. Smee, who placed his own collection of microscopical slides 

 of aphides and of diseased potatoes, mounted by himself during the potato 

 murrain in 1845-1847, in that gentleman's hands for examination. 



Through the kindness of Mr. Worthington Smith, 1 am enabled to 

 give the following woodcuts of one of the microscopical preparations of 

 Mr. Alfred Smee's own collection, mounted by himself, of the Aphis vastator 

 and of a slice of diseased potato. The Aphis vastator is here enlarged 

 twenty diameters, and the minute fungus fruits are to be seen inside the 

 insect at A, B, c. 



These bodies belonging to the fungus are further enlarged on the 

 margin of the cut to 160 diameters, so that their nature may be better seen. 

 Some of Mr. Smee's aphides are completely filled with the fungus inter- 

 nally, and covered with it externally; and though Mr. Smee did not 

 completely understand the meaning of the fungus (at a time when it had 

 not yet been described), yet it is clear that he saw the fungus on the 

 insect, for some of the slides are scratched with a diamond and marked 

 " fungi." As far as we know, no one but Alfred Smee had detected aphides 

 in this peculiar state of disease, and we believe the condition is unknown 

 even now to most entomologists. 



If any further proof had been wanting as to the identity of the 

 bodies found in the potato with those in the aphis, it was supplied by the 

 behaviour of Mr. Smith's secondary form of fruit when (after a whole 

 year's rest) it germinated. Mr. Smith found on germinatien that the 

 spores grew equally well on vegetable as on animal matter. 



It should be here observed that in Mr. Smee's book on the Potato Plant 

 it will be seen that a chapter of that work is devoted to the various kinds 

 of fungi which are to be found on diseased potatoes, and there are several 

 lithographic plates illustrating this subject. On plate 3, fig. 7, is a 



