SECTIONAL TRANSACTIONS.— K. 501 



Miss P. E. Thomas. — The phycomycete flora of Glamorgan ; the Mono- 

 blepharidales (3.20). 



In 1935 an investigation of the species occurring in the vicinity of Cardiff, 

 Glamorgan, was begun and all the six species of which the full life history 

 has been described were found growing together in one locality. Subse- 

 quent collections from this and other localities in the same area have also 

 yielded these six species. 



The six species described are : M. spheerica, M. macranda, M. polymorpha, 

 M. brachyandra, M. fasciculata and M. insignis. Particular attention has 

 been paid to M. fasciculata and M. insignis since these two species have not 

 been recorded since they were originally described by Thaxter in 1895. 

 M. polymorpha and M. brachyandra, although new British records, have 

 previously been described from other European countries and from America. 



Investigations have shown that the type of substratum on which the 

 organisms grow is of comparatively little importance, for although it had 

 previously been suggested that they occur most commonly on ash and 

 birch twigs, this has not been found to be true and species have grown on a 

 variety of woods, the consistency of the wood being apparently of greater 

 importance than the species. Temperature is an important factor in the 

 cultivation of the fungus and a period of cold immediately following collec- 

 tion appears to be essential for the production of active growth. Under 

 suitable control of temperature it had been possible to grow the species 

 under laboratory conditions and investigate their life-histories. 



Dr. J. Caldwell and Mr. A. L. James. — hwestigattons into stripe disease 

 of the Narcissiis (3.50). 



In the spring of 1936 a study of the " Stripe " disease of Narcissus was 

 begun at Exeter. Diseased plants of different varieties were collected and 

 examination revealed the fact that our main types of symptoms can be 

 recognised in different varieties. Briefly, the main symptoms are either 

 a mosaic or an hypertrophy of the plant tissues leading to the formation of 

 proliferations on the surfaces of leaves and of flower stalks. A study of the 

 diseased tissues has shown that the two types of symptoms are probably 

 closely related histologically. 



In the spring of 1937 preliminary inoculations were made and this year 

 symptoms of the disease were well developed on the inoculated plants. 

 This spring, further inoculations were made which indicate that the causa- 

 tive agent is a virus and that the different symptom-pictures are conditioned 

 by the variety rather than by the virus. 



Experiments are being carried out on the identity of the virus and on the 

 method of spread in the field. 



Tuesday, August 23. 



Discussion on Present aspects of plant virus research (lo.o). 



Dr. K. M. Smith and Mr. W. D. MacClement. — On the natural 

 modes of dissemination of certain plant viruses. 



Until recently it has been generally assumed that most, if not all, plant 

 viruses are dependent upon one or more insect vectors for their dissemina- 

 tion in the field. The fact that the mode of spread of a number of viruses 

 was unknown was explained by the suggestion that the particular insect 



