ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 645 



The nuclei both of the antheridium and trichogyne, after anastomosis 

 of these two cells, degenerate without fusion. The antheridium 

 occasionally gives rise to a chlamydospore or to a perithecium. 



In a further account * of Pyronema confluem the writer affirms the 

 same conclusion, that though antheridium and trichogyne are present 

 and anastomose they are functionless, and that the ascogenous cell is cut 

 off from the trichogyne and produces the ascus-bearing branches without 

 any nuclear fusion. 



Infection-Powers of Ascospores in Erysiphacese.t — E. S. Salmon 

 describes his experiments to test Neger's theory that though the conidial 

 stage of Erysiphe Qraminis represented a biologic form confined to one 

 host, the ascospores would prove to be the connecting link between 

 different host-plant species. He used in each case the perithecia of the 

 fungus from barley. The leaves covered by the fungus had been kept 

 dry daring the winter. On being placed in suitable conditions the asco- 

 spores developed, the perithecia burst open and they were ejected on to 

 the glass cover of the Petri dish forming the moist chamber. From 

 this material Salmon infected seedling plants of barley, oats, wheat, and 

 rye. Repeated experiments resulted in the production of a plentiful 

 growth of the Oidium on the barley plants. In no case, we gather, did 

 any of the other plants take the infection. 



In a further communication % he records the results of a number of 

 experiments on plants of several species of Hordeum, and proves con- 

 clusively that in the case of this fungus " biologic forms " are present 

 in the ascigerous stage as well as in the conidial forms. Many in- 

 teresting observations on the germination of spores are made and on 

 infection methods. 



The same author § finally sums up the results of his study of the 

 specialisation of parasitism in the Erysiphaceas, and the extent to which 

 the spores of the fungus will infect different hosts. He proves satis- 

 factorily the existence of biologic forms in the species ; and gives tables 

 of the time, temperature, &c, of the different infections. 



Em. Marchal || has conducted experiments on similar lines and arrives 

 at very similar conclusions. He infected the same host-plants with the 

 conidia and with the ascospores, and the results corresponded in each 

 case, proving the fixed character of the biologic forms. 



Influence of Substratum on Germination of Spores of Peni- 

 cillium.^f — P. Lesage experimenting with cultures of PeniciUium 

 glaucum on drops of gelatin or nutritive jelly, concludes that the 

 germination of the spores is influenced by the substratum ; that the sub- 

 stratum formed by the jelly of old cultures is unfavourable to the 

 germination of new spores ; and that exposure to dry air for some time 

 modifies such substratum so that it is no longer unfavourable to the 

 germination. The nature of the modification is subject for future 

 investigation. 



* Tom. cit, pp. 1335-36. + Journ. Bot., xli. (1903) pp. 159-65. 



X Tom. cit, pp. 204-212. 



§ Beih. Bot. Centralbl., xiv. (1903) pp. 261-315 (1 pi. and 6 figs.). 

 || Comptes Rendus, cxxxvi. (1903) pp. 1280-81. 

 i Trav. Scient Univ. Rennes, i. (1902) pp. 171-4. 



