626 EXPERIMENT STATION RECORD. 



prevailing in tlie fall and sjn-iug, wliieli are the natural periods for the best 

 seed germination. 



Variation of fungi due to environment, F. L. Stevens and J. G. Hall {Bot. 

 Gaz., JfS {1009), A'o. /, pp. 1-30. figs. 31). — Attention is called to the variation 

 found in studies of fungi made during the past few years, and attempts were 

 made to analyze the cause of the variations to the end that the factor of 

 environmental variation may be more clearly recognized as a problem in mycol- 

 ogy. The effect of density of colonies, density of mycelium, chemical rela- 

 tions, light relation, and several unknown factors are discussed at length, and 

 the variability in spore measurements due to various factors is shown by 

 means of diagrams. 



The authors state that the bearing of these facts on mycological taxonomy is 

 apparent, and that the tendency to variation should be recognized In making 

 studies of many fungi. They believe that many fungi should be studied in 

 cultures, under suitable standard conditions, in order to determine some of 

 their more important taxonomic characters. 



Notes on Peronosporales for 1907, G. W. Wilson {Proc. Iowa Acad. tSci., 

 15 (1908), pp. 85-S9). — Studies were made of various genera and species of 

 mildews to determine the interrelation of meteoi'ological conditions and the 

 development of these fungi, and also the location of centers for seasonal distri- 

 bution. Sixteen species have been under observation, represented by 72 speci- 

 mens, and of these only S contained oospores. The seasonal distribution 

 showed that Plasmopara pygmwa is an early spring form, and Bremm lactucw, 

 Peronospora euphorhia', antl P. patciitilUr early summer forms, while Albugo 

 portulacw, A. tragopogonis, Rhysofliccd halstcdii. Peronospora cffusu, and 

 P. poJygoni appeared during the latter part of the summer and in autumn. 



Synopsis of the British Basidiomycetes, VV. G. Smith {London, 1908, pp. 

 531, pis. 5, figs. 145). — The publication is designed as a handboolv for the 

 study in the field of the larger British fungi, and a descriptive catalogue is 

 given of the drawings and specimens in the department of botany of the 

 British Museum. More than 2.000 species are described, including those grow- 

 ing in the open air and those constantly appearing in greenhouses and in 

 gardens. The term Basidiomycetes is used in the same sense as it was em- 

 ployed by Debary, and includes all mushroom-like fungi, the forms growing 

 on stumps and trees, puff balls, etc., but not the rust fungi which are included 

 by Brefeld. 



The effect of chemotropism on the parasitic action of fungi, L. Petri {Atti 

 R. Accad. Lincei, Bend. CI. Sci. Fis., Mat. e Nat., 5. scr., 18 {1909), I, No. 10, 

 pp. 545-553, flgs. 3). — Experiments with a number of species of grasses are 

 reported in which their susceptibility to the fungus Sclerotinia lihertiana was 

 investigated. 



The author found that some species of grasses possess a natural immunity 

 against this fungus while not showing ininumity against the citase elaborated 

 by the fungus. He is led to believe that immunity against parasitic organisms 

 on the part of the plant is based on the minimum content of nutritive substances 

 in the aerial organs that exercise a positive chemotropic stimulus upon the 

 fungus sufficient to produce citase and of the presence of sufficient oxalate of 

 potash to overcome the neutralizing action of the cellular content of the higher 

 plant. 



The author thinks that in the cases studied, and probably in many others, 

 natural immunity against parasitic micro-organisms is secured through the 

 occurrence in the various organs of a minimum stimulating action and a maxi- 

 nnim neutralizing effect of the enzymic activity of the parasite. In those plants 

 whieli are Incking in antienzymic i)ower natural immunitv is wanting. 



