SCIENTIFIC COMMITTEE, AUGUST 5. 



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simply a naked name, with no claim to recognition, except by the small 

 woodcut of one of its supposed species and the meagre information which 

 accompanies it. From this woodcut it appears that the small conidia 

 resemble those of Phoma, being minute and binucleate, produced on 

 sterigmata from each cell of triseptate, clavate sporophores, and that 

 these sporophores are arranged concentrically in oval tufts, which are pre- 

 sumably superficial. Hence we are led to the conclusion that there are 

 no perithecia and that the fungus is allied to the Hyphomycetece, but 

 whether to the Mucedinece or the Dematiece there is no indication ; possibly 

 the former, as no coloration is mentioned. Under these circumstances 

 Allescheria remains still a problematical genus, and Allescheria laricis an 

 imperfectly described species, or really — as I should term it— a nonde- 

 script. It is a great pity that these manuscript names should be recog- 

 nised at all, as their quotation leads, as in this instance, to endless 

 trouble. Subsequently I made a journey to Kew and consulted my 

 colleague, Mr. George Massee, and found him involved in just the same 

 mystery, for he had sent direct to Germany for specimens of the authentic 

 Allescheria laricis, and had received what were supposed to be such, but 

 he confessed that he could find nothing which resembled the woodcut, 

 and was as far as ever from the solution of the mystery." 



Silver-leaf Disease. — Dr. Cooke, V.M.H., contributed the following 

 account of its explanation : " Professor John Percival has communicated 

 an interesting and valuable contribution towards elucidating the mystery 

 of the Silver-leaf disease to the Linnean Society (Journal, Botany, 

 No. 245, July 1902). He states that the peculiar ashy-grey colour 

 of the leaves is caused by large intercellular spaces, filled with air, 

 which are present beneath the cuticle along the lines of union of the 

 epidermal cells. How these air channels are produced is not clear at 

 present. No spots or blisters are visible, and fungi are absent from the 

 leaves and tissues of the stem and branches. In advanced cases a dis- 

 coloration of the central parts of the wood is observable when the stems 

 are cut across, i^arge roots of long-diseased trees were found to be 

 similarly affected. Examination of the discoloured wood revealed the 

 presence of fine fungus hyphas. Segments of diseased roots placed in a 

 damp chamber in two or three days developed a dense white mycelium 

 round the edge of the diseased patch. In other specimens of Plum and 

 Apricot trees affected with silver leaf the wood of the root invariably 

 showed internal discoloration, and fungus hyphae were always found in 

 the wood near the junction between the living and dead portions. At 

 first no conidia were found upon the mycelium, but after three or four 

 months' growth small sporophores of Stereum purpureum appeared upon 

 pieces of root. In one case only the fully-developed fruiting stage 

 of the Stereum has been seen on diseased trees. The appearance of 

 this specimen is described, with its discoloured wood, and the inference 

 that the Stereum was in some way responsible for the Silver-leaf 

 disease. Then follow details of the inoculation of healthy Plum-trees 

 with the sporophores of Stereum purpureum, and in eight or nine weeks 

 after the leaves exhibited the characteristic silvery appearance. From 

 these experiments it would appear that the disturbing cause is conducted 

 rapidly in the sap of the plant. From the evidence it appears that the 



