93 



TV est of England jn connection with the extensive damage 

 •caused by Silver Leaf. The method of infection, effect oi soil- 

 conditions, and especially the question of stocks, were studied 

 in the field. All the most recent researches, both in the orchard 

 and in the laboratory, tend to confirm the view that the difl e 

 in the vi -i majority of ca-es is caused by Stereum fmrpureum, 

 which gains entrance to the tree through wounds. A lecture 

 r was given at AVorcester and also demonstrations showing method 



of injection and destruction of the trees by tiie attacking fungus. 



Technical advice has also been supplied to the Horticultural, 

 Technical, ami Supplies Divisions of the Food Production 

 Department, and also to the Seed Testing Station of the Board 



•of Agriculture and Fisheries with regard to various fungi affect- 

 ing particularly seed wheat. Some sixty sample- of Hie Latter 

 have been received for investigation. Amom i ihe fungi found 



is an interesting Pyrenomycete, the development of which U 

 being investigated by Mrs. Alcock. 



II. Research. 



Botrytis. — The investigation 



Mi. W. 



B. Brierley was continued. The work developed along two 



mam 



the 



the fungus in the tissues of various hosts, it was ascertained 

 that under certain condition- the hyphae may absorb their cell- 

 walls and exist in a free plasmodial state, the fungus passing 

 thus from cell to cell through the pits in the walls. 



The second line of work has been the investigation of the 

 variability and specific constancy of the morphological and 

 physiological "characters of the fungus when growing unde 

 exactly controlled environmental conditions. A very great 

 amount of data has been obtained, but the investigation is still 

 far from complete. It is clear, however, that B. cinerea, is not 

 a single species, but an aggregation of numerous elemen- 

 tary species; the morphological characters of any particular 

 culture or growth of this fungus being a direct resultant of two 



factors, viz., the elementary species and the host or culture 

 medium. Within certain limit-, therefore, the morphological 

 characters of specific value of the fungus are under the control 

 of the investigator, and may be changed at will. 



Rose Blotch Fungus. — The life-history of the Rose Blotch 

 fungus was investigated by Mrs. Alcock and a new method of 

 hibernation similar to that which occurs in Apple and Pear Scab 

 was discovered. The results were published in the Bulletin 



1918, p. 193). 



Onion Disease. — In conjunction with Miss Owen, research on 

 the biology of the onion Sclerotium disease was continued. The 

 name Sclerotinia bulborum, under which the disease has recently 

 passed, was found to be incorrect, the fungus in reality being 

 Sclerotium cepivorum, Berkeley. The parasite was shown to 

 attack the plant by means of the roots and to spread upwards to 

 the base of the bulb. It form- both spores and sclerotia on the 



