350 EXPERIMENT STATION EECOKD. [Vol.38 



the country, those in which it has reached neighboring countries only, and those 

 in which it is still confined to areas isolated by the ocean or large tracts with 

 climate and vegetation unfavorable to the spread of the disease organism. 



As illustrative of the probable means of introduction of foreign species, the 

 rusts of Australia are taken, some 27 of which are treated as introduced spe- 

 cies and are discussed in connection with their hosts and several modes of in- 

 troduction. Tlie work of the International Phytopathological Convention held 

 in Rome in 1914 is discussed in this connection. 



Report of the botanist, S. M. Bain {Tennessee Sta. Rpt. 1915, pp. 118-120).— 

 A summary report is given of investigations carried on by the department of 

 botany on the selection of pear and apple seed for blight resistance, the phy- 

 siology of the resistance of clover to Colletotrichum, and the resistance of 

 Spirogyra to various fungi. The work with the pear and apple has only been 

 begun, extensive plantings of seed from different sources having been made. 



In the studies of clover resistance the maximum temperature endured by 

 Colletotrichum spores Avas found to be about 45° C. (113° F.), the spores being 

 killed by a moment's exposure to that temperature. This is believed to ex- 

 plain why so many samples of spores taken in the field during the season failed 

 to germinate. Preliminary experiments indicate that infection of clover occurs 

 much more readily in tissues in an actively growing or meristematic condition. 



Experiments with Spirogyra are reported upon, Spirogyra having been se- 

 lected as a convenient host plant for microscopical study. Three or four dif- 

 ferent fungus diseases of Spirogyra have been found and studied to some ex- 

 tent, the fungi being obligate parasites, facultative parasites, and saprophytes. 

 The results of a microscopical study of the methods of attack showed that 

 Pythium infects by zoospores, large numbers of which collect on Spirogyra cells 

 that have just died. They do not collect upon living cells or upon cells long 

 dead. Infection always starts at a dead cell. The advancement of the my- 

 celium through the Spirogyra filament is said to take place with great rapidity, 

 as many as seven cells having been killed in an hour by a single filament of 

 Saprolegnia. 



[Plant diseases in Barbados], J. S. Dash {Rpt. Dept. Agr. Barbados, 1915- 

 16, pp. 35-40). — The most notable sugar cane trouble observed during this 

 period was that known as the pineapple disease {Thielaviopsis paradoxa {T. 

 ethaceticus) ) . No connection was established between this fungus and 

 Melanconium sacchari, the cause of rind disease. Colletotrichum falcatum was 

 not present to any considerable extent. 



Examination of a new disease of sugar cane showed that the last-named 

 fungus was often present with a Cephalosporium, which was studied and is 

 herein discussed at some length. The disease does not seem to attack canes 

 growing under very favorable conditions. Its progress is slow. Destruction of 

 rotten canes and selection of plant material are expected to control the disease. 



Cotton suffered severely only from leaf spots and mildew during this period. 

 A branch disease of pigeon pea is ascribed to a Colletotrichum. Examination 

 of dying sorrel plants showed a species of Gloeosporium, and a second species 

 was found to cause a dieback and leaf cast in a single breadfruit tree. 



Plant protection in Switzerland, F. G. Strebler, A. Volkart, and A. Grisch 

 {Scluceiz. Samen Untersuch. n. Versnchsanst. DerUkon-Ziirich, Jahresber., 39 

 {1915-16), pp. 23-28). — This portion of the report deals briefly with diseases of 

 cereal crops, potatoes, beets, legumes, and forage plants, also with nematode 

 attack and weed pests. 



[Plant diseases in India], J. Mackenna {Rpt. Prog. Agr. India, 1915-16, pp. 

 46-50). — It is stated that the most important disease under investigation at 



