NOTES AN£) ABSTRACTS. 



?83 



■of' climatic conditions for the years 1907-1908, and enumerates various 

 fungoid diseases which have come under investigation during those two 

 years, and further observations on diseases previously recorded. The 

 ' Peach apparently suffered more than any other crop from both fungoid 

 and physiological diseases. The probable causes of peach-yellows, or 

 so-called peach-yellows, are then discussed. There are no less than 

 four different theories as to the cause : — ■ 



1. Winter injury. 



2. Lack of potash in the soil. The analysis of peach wood suffering 

 •from yellows showed a lack of potash. 



3. The presence of some deleterious enzyme in the plant. 



4. Germ theory, i.e. that the trouble is bacterial, although so far 

 no definite organism has been found. Careful cultivation and the appli- 

 cation of potash manures are suggested as preventives. 



The second half of the report is taken up with an account of the 

 investigations with regard to (a) the chestnut-bark disease, Diaporthe 

 parasitica, which is doing so much damage to the chestnut trees in 

 America, especially in the Eastern States ; and (b) a paper on Artificial 

 Cultures of Phytophthora, with special reference to oospores. 



It was reported by Flora W. Patterson that the chestnut-bark 

 disease was due to a Cytospora, but Dr. Murill found Cytospom to be 

 the conidial stage of an ascomycete Diaporthe parasitica. It attacks 

 chestnut trees of all ages. Old trees begin to die from the top down- 

 wards. On young trees and on the sprout growth, cankered areas show 

 in the apparently healthy bark, and not infrequently girdle the tree. The 

 presence of these cankered spots on the entirely smooth bark a^ords the 

 best evidence that the disease is due t5 a fungus, an'd not entirely to 

 winter injury followed by Cytospora, as some investigators were led 

 to believe. The author is uncertain whether fruiting bodies of the 

 fungus are developed on the cankered spots the first year, and this 

 may explain why so many cankered spots show no fruiting bodies. 

 On some, however, fruiting pustules develop in the summer in the 

 form of tentacles, light orange-brown, but by the winter becoming dark 

 "chestnut-brown. The fungus has two spore stages, both of which 

 develop in these pustules. The Gytospora stage usually appears during 

 the autumn and coiitinues into the spring. In the latter part' of 

 "December the second, or winter, spore stage develops. The spherical 

 '^pore receptacles are formed in the tissues at the base of the pustule 

 and round its margin; they open to the exterior by long slender 

 necks, which can be seen- as small black spots on the surface. The 

 asci contain eight oval to elongated ascospores., usually arranged in 

 a single row. The spores are shed in winter and early spring. Artificial 

 cultures were made on Lima bean agar, but the Cytospora stage alone 

 .developed. The writer is led to believe that winter injuries and summer 

 droughts are important factors in handicapping trees against the depre- 

 dations of the disease, and that the nature of the fungus is not such as 

 .to place it amongst the virulent parasitic forms. Metcalfe, however, 

 believes that it is a virulent parasite, and that unless something inter- 



