646 EXPERIMENT STATION RECORD. 



In addition to the above, notes are given ou leaf spot due to Cephalosporium 

 sp., a root and trunk disease associated with the presence of Fusarium sp.. and 

 the attaclc of nematodes {llcterodera radicicola). 



For the leaf rot no satisfactory method of control has been found, although 

 spraying with I'.ordenux mixture will lessen the disease to a considerable extent. 

 For the leaf spot Bordeaux mixture is usually found quite effective if thoroughly 

 applied. For the control of the spot on berries the author recommends pro- 

 viding adequate shade, as this not only renders the action of the fungus less 

 harmful, but also impi-ove the quality of the coffee. For the root diseases ditch- 

 ing about the trees, together with the use of unslaked lime, sulphur, or other 

 substances about them is recommended. 



Black root disease of limes (Agr. News [Barhados], 13 {191Jf), No. 327, pp. 

 SG-'i, 365). — This is the mycologist's report, continuing observations of South 

 (E. S. R., 26, p. 245; 28, p. 149), on Rosrllinia hunode?. altacking lime trees in 

 Dominica. 



This important disease is said to be different from one somewhat similar on 

 cacao. It appears only on estates with fairly recent forest clearings, ajiparently 

 preferi'ing trees growing under very good conditions. New roots which often 

 appear above the wound on the collar may remain healthy for a time and lead 

 to partial recovery of the tree. The fungus remains active on roots and branches 

 in the soil, attacking new roots and following these to the collar, and extending 

 up the tree if dampness and shade are abundant. 



Spores of two forms occur on the above-ground portions (the later form being 

 the more resistant), but it is thought that infection usually occurs by contact 

 of live portions with dead roots bearing the fungns. 



The wet weather of the year is thought to account in part only for the serious- 

 ness of the situation, the natural spread of the roots playing an important part. 



Remedial measures suggested include the use of carbon bisulphid emulsion as 

 adA'ocated by Bordnz (B. S. R., 31, p. 549), isolation by means of trenches, 

 ventilation, destruction by fire of all affected wood, and budding on sour orange, 

 which is said to be immune to this fungus. 



Black knot of birch, G. Massee {Roy. Bot. Gard. Kew, Bui. Misc. Inform. 

 No. 9 (1914), pp. 322, 323, fig. 1). — It is stated that Plmcrightia virgultorum 

 is the cause of a disease found on birch trees in parts of Scotland. England, 

 Sweden, Switzerland, Finland, and Germany. The disease is described, in its 

 several stages. 



Removal of infected branches is the only remedy suggested. 



The relationship of Endothia parasitica and related species to the tannin 

 content of the host plants, M. T. Cook and G. W. Wilson {Ahs. in Science, n. 

 ser., Jjl {1915), No. lO.'/S, pp. 171, 172). — Two strains of E. parasitica (one 

 American and the other Chinese), E. radicalis, and E. radicalis niississippirnsis 

 were grown in culture media to ^^■hich different percentages of commercial 

 tannin and special extracts were added. 



The results of the experiments indicate that the commercial tannins are 

 variable and probably not pure tannin ; that ordinary commercial tannin and 

 pure tannin extracts are not the same; and that the form or quantity of tannin 

 or tannin-like substances with which the fungus comes in contact in the host 

 plant is not known. The food supply influences the vigor of the fungns and its 

 power of resistance. High percentages of tannin usually cause a retardation of 

 germination, frequently followed by an abnormal growth of aei'ial mycelium. 

 E. radicalis mississippiensis was found most resistant, E. parasitica second, and 

 E. radicalis third, and the American strain of E. parasitua was more resistant 

 than the Chinese strain. 



