852 EXPERIMENT STATION RECORD. 



operative in gummosis (E. S. R., 23, p. 353; 24, p. 554), the author holds that 

 stimuli, such as frosts and wounds, only accentuate a natural tendency latent 

 in cherry and other trees to gummy degeneration and related phenomena due 

 to variations in growth and nutrition which may be regarded as not abnormal. 

 These may result in cell immaturity, unbalanced tensions, excess of enzyms, 

 and degeneration processes extending from cell to cell. Such groups of de- 

 generated cells are usually more abundant in the late fall growth. Looseness 

 of structure appeared to be closely related with susceptibility to frost influence 

 and formation of gum. 



Detailed studies were made of numerous widely separated genera of trees. 



The Pennsylvania Chestnut Blight Conference {Harrisdurg: State, 1912, 

 pp. 253, pis. Jf3). — This is a report of the proceedings of a conference, called by 

 the Governor of Pennsylvania to meet at Harrisburg, Pa., February 20 to 21, 

 3912, to consider ways and means of preventing the spread of the chestnut tree 

 bark disase. An address by the governor, and numerous papers, reports and 

 discussions by scientists, foresters, manufacturers, and others, bring out what 

 was known at that date and what it was considered should be known concern- 

 ing this disease. 



Notes en the chestnut bark disease, H. R. Fulton (In Pennsylvania Chest- 

 nut BUglft Conference. Harrisburg: State, 1912, pp. ^8-56). — The author 

 reports on a study of the means, methods, and conditions of transmission of 

 this disease, in substance briefly as follows: 



The infective material in case of Diaporthe parasitica consists in its conidia 

 and its ascospores. Tests made with air currents as carriers of conidia, dry, 

 damp, and under strong spraying to simulate storm conditions, showed that 

 conidia can be detached by strong air blasts and carried, short distances. 

 Conidia in a dry room at ordinary temperature, retained their germinability 

 for four months, but not for five, while material exposed out of doors and that 

 kept moist at about 75° F. in a greenhouse did not germinate after four months. 

 Both kinds of spores germinated in a decoction of chestnut bark, in rice broth, 

 etc. Ascospores germinated in spring water, while conidia did not. Germina- 

 bility of conidia is most favored at 60°, decreasing considerably at 10° above 

 or below that point. Ascospores germinated best at 70°, but also fairly well 

 at 45° or 85°, and they still germinated readily after at least moderate freezing. 

 The effect of extreme temperatures was not investigated. In general, the 

 most rapid early growth is at the optimum temperature for germination. 



In the laboratory the fungus grows well on a variety of artificial media, 

 particularly on a slightly acid potato agar. Some evidence seems to point to 

 the possibility of its living on at least dead parts of trees other than chestnut, 

 as oaks, etc., though such have not been shown to be diseased by the fungus. 

 Infections were found where injuries to chestnuts had been inflicted by light- 

 ning, etc., both sapwood and heartwood becoming infected by spreading of the 

 fungus if the cut surface was kept moist. Insect injuries also appeared to be 

 favorable points for development of infection from spores. Field studies at 

 Orbisonia. Pa., seem to indicate that there had been a very rapid spread of the 

 disease recently ; that insects may carry infection up the branches and into the 

 cracks and holes ; that moisture favored infection in certain cases ; that younger 

 trees were more susceptible than older ones ; and that birds were not notably, 

 if at all, connected with the carrying of spores. 



[Longevity of mycelium and spores of Diaporthe pai*asitica], Caroline 

 RxJMBOLD (In Pennsylrania Chestnut Blight Conference. Harrisburg: State, 

 1912, pp. 2Jil, 2}i2). — An attempt was made to germinate spores from an in- 

 fected piece of chestnut collected in July, 1908, and kept continuously in a 

 moist cell until April, 1912. The fungus made a small growth, but after start- 



