460 BOTANICAL GAZETTE [December 



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lure, 23"-25''C. Attempts to isolate the mould with B. Anthracis or a pink 

 yeast resulted negatively. — Mary Hefferan. 



An important contribution to the subject of the relation of parasite 

 and host among the plant-rusts has been made by Professor H. Marshall Ward" 

 in the Annais of Botany, The summer (uredo) spores of brown rust were sown 

 upon seedlings of all available species of grasses belonging to the genus Bromus. 

 The spores were obtained from Bromiis inollis^ B, sterilis, and B. secalimis. 

 The result in general was the infection of most species belonging to the 

 section of the genus which included the host from which the spores were 

 taken, and not of species belonging to other sections of the genus. 



The author undertook to find out if any anatomical or morphological 

 differences existed in the hosts which might account for the immunity of 

 some hosts and the susceptibility of others to the attack of the rust, and in so 

 doing developed a wealth of data regarding the number of stomataand hairs 

 per given area, the size of stomata, the number of leaf ribs and distances 

 between them, the comparative area of chlorophyll tissue, and many other 

 details that must challenge the admiration of every investigator. Each set 

 of data is compared with the " curve of infection " and the charts so con- 

 structed show with great clearness that no correspondence exists. The 

 discussion of these data touches upon many points that can not be mentioned 

 here, but is most lucid and convincing and ends with the statement, that "we 

 are driven to conclude that the factors which govern predisposition on the one 

 hand, and immunity on the other, are similar to those which govern fertility 

 and sterilty of stigmas to pollen.*' It is, therefore, to be referred, so far as 

 we can now judge, to the quality of nutriment afforded by each host, including, 

 doubtless, some less evident factors. 



In carrying on the work it was found necessary to institute an investiga- 

 tion into the characters and limitations of the species of Bromus, and consid- 

 erable information regarding the seeds and seedlings especially is given. 



Of conditions that inhibit the development of the rust, temperature was 

 found to be the most important, the upper and lower limits being about 27"" 

 and 10° C. respectively. The presence of green algae, or the spores of molds 

 and other fungi, had no perceptible effect on the germination of the rust 

 spores, neither did the presence or absence of light. 



Although the paper is notable for the breadth and thoroughness of the 

 observations, it is even more important for the cleat and far reaching conclu- 

 sions that are drawn from the data. It will do much to throw light upon an 

 intricate and obscure subject. — J. C. Arthur. 



Dangeard " has recently published an extensive account of the Eugleni- 

 neae. The material is very poorly arranged, without index or even a suitable 



^' Ward, H. Marshall, On the relations between host and parasite in the bronies 

 and their brown rust, Puccinia dispersa (Erikss.). Ann. Botany 16: 233-315- ^902- 



" P. A. Dangeard, Recherches sur les Eugleniens. Le Botaniste VIII. fascs. 3-6, 

 97-370, ph. 4. figs, 33, 1902. 



