474 SUMMARY OF CURRENT RESEARCHES RELATING TO 



great variation to be found as to the number of nuclei in the cells of 

 Ascomycetes and in other fungi in closely related forms. 



Willow Canker.* — So long ago as 1899 specimens of diseased rods 

 from the osier-beds in Connemara have been sent to Dublin for examina- 

 tion. T. Johnson, who has recently had opportunities of visiting the 

 district and seeing the extent of the disease, now gives an account of its 

 origin and spread, and the methods he considers best for destroying the 

 fungus. The plants had been infested when they were first planted. 

 The disease, due to a Pyrenomycete, Physalospora gregaria Sacc, appears 

 as black specks or canker-spots on the rods, destroying the tissue and 

 causing the rods to break at the damaged areas. Besides the ascosporous 

 stage there are two other forms, which he calls Tetradia salicicola and 

 Macrodendrophoma salicicola, both pycnidial stages of the fungus. All 

 three forms propagate the disease. Formalin has proved a good fungi- 

 cide. Burning: of all diseased sets is recommended. 



V- 



Specialisation of Parasitism in the Erysiphacese.f — E. S. Salmon 

 has carried out a further series of experiments in connection with his 

 study of biologic species of parasites. He has proved that the results of 

 the inoculation experiments are the same, whether he works with asco- 

 spores or with the conidial forms. The recent experiments were made 

 with the conidia of the biologic form of Ergsiphe graminis on wheat. 

 With these he successfully infected young leaves of Hordeum silvaticum, 

 and kept the fungus growing through five generations ; after that the 

 conidia readily infected wheat, while their power of infecting their 

 original host had not been weakened. Another discovery was that the 

 successive generations had a weakened power of infecting Hordeum 

 silvaticum. The spores seemed to lose vigour away from their normal 

 host. Throughout this experiment only young leaves could be success- 

 fully infected. 



Research on Yeast.J — W. Henneberg has been experimenting with 

 yeast cells to test life duration and the effect of foreign organisms in 

 the cultures, etc. He concludes that the duration of vitality depends 

 largely on the " race " ; some races being specially long-lived. . A some- 

 what low temperature is conducive to longevity ; at 30° the cells persisted 

 only a week, at 10° they lived for about four weeks, also on the surface 

 of a large mass the cells persist longer than those deeper down. The 

 readier access of oxygen would account for the difference. In all cases 

 some few cells would be more vigorous and resistant than the bulk of 

 the culture. Certain bacteria have a fatal effect, such as the bacteria 

 of lactic acid and of acetic acid. Other bacteria are harmless. 



Hyphomycetes.§ — G. Lindau concludes in this fourth part the 

 description of Gliocladium begun in the third part, p. 176. He then 

 follows with the Botrytidere, under which he includes all those forms 



• Sci. Proc. Roy. Dublin Soc, x. (1904) pp. 153-66 (3 pis.). 



t Ann. Mycol., 'iii. (1905) pp. 172-84. 



\ Wochensch. Brauerei, Nos. 41-8 (1904) 46 pp. ; published 1905. See also 

 Hedwigia, xcviii. (1905) p. 106. 



§ Rabenhorst's Kryptogamen-Flora, I., Abt. viii. Pilze, Lief 95, Leipzig, 1905, 

 pp. 177-256. 



