416 SECTIONAL TRANSACTIONS.— K. 



Friday, September 11. 



Dr. C. E. Foister, Mr. I. W. Tervet, and Mrs. N. L. Alcock.— A 

 contribution to the study of rots in potato storage (io.o). 



A storage rot of potatoes much resembling Dry Rot (Fusarium cceruleum) 

 but caused by a pycnidial fungus has recently been investigated. The early 

 symptoms of the disease consist of small depressions, the later stages of 

 large, intact or wrinkled areas. A large internal rot develops, often with 

 large cavities which are lined with mycelium in which are embedded the 

 black pycnidia. Using single spore cultures, the disease has been produced 

 in various commercial potato varieties. Early varieties are more readily 

 affected and the disease is more prevalent in boxes or bags than in clamps. 

 The disease has been present for a number of years but its resemblance to 

 Dry Rot has caused it to be classified as the latter disease. The fungus 

 belongs to the Phomacece and is possibly new to science. 



Dr. J. Caldwell. — Recent work on the nature of virus (10.30). 



The aspect of the problem of virus diseases in plants which has been 

 most studied recently is the nature of the causative agent of the disease. 

 A crystalline protein has been shown to be associated with the disease of 

 Mosaic of Tobacco (Tobacco Virus I) and attention has been focussed on 

 the relation of this protein to the agent of the disease. The mode of in- 

 fection with the virus of this disease has been re-examined and evidence is 

 adduced to support the view that infection by means other than through 

 broken protoplasts is rare. The age of the leaf at the time of inoculation 

 and the amount of growth made by the leaf at the time of inoculation are of 

 primary importance. A method is discussed which allows of the study of 

 the effect of substances on the virus without confusion with the effect of 

 these substances on the host tissues. 



Dr. M. Noble. — Heterothallism in Typhula Trifolii (11. o). 



In Typhula Trifolii the haploid hyphae have plain septa and usually one 

 nucleus in each cell, the diploid possess clamp connections at most of the 

 septa and usually one pair of conjugate nuclei in each cell. Anastomosis 

 and migration of nuclei occurs in haploid and in diploid mycelia where there 

 is no question of diploidisation. 



Monospore cultures sometimes produce haploid sclerotia and fructi- 

 fications. The latter are smaller than the diploid and produce small fertile 

 spores. 



When anastomosis occurs between compatible haploid mycelia, migration 

 of nuclei takes place followed by upsetting of the equilibrium of the cells of 

 the invaded hypha, in which some of the indigenous nuclei disintegrate. 

 Nuclei migrate by the partial or complete dissolution of the transverse 

 septa ; where partial dissolution takes place half walls are produced and at 

 these the side wall may bulge out. When the invading nuclei have reached 

 the younger parts of the hyphae they conjugate with the indigenous nuclei 

 and, on the division of these conjugate pairs, clamp connections are 

 produced. 



The work of Lehfeldt on Typhula erythropus is thus confirmed. The 

 significance of this confirmation is discussed with reference to recent work 

 on the diploidisation of Coprinus. 



