RECENT ADVANCE IN THE STUDY OF FUNGI 533 



extend our knowledge to closely related forms. The constantly 

 accumulating mass of evidence must, by this time, have con- 

 vinced the most sceptical as to the increased range of sexuality 

 in the ascomycetes. It has been proved by Harper to be 

 present in the genera Sphcerotheca, Erysiphe, and Pyroncma. 

 Claussen has worked it out in Boudiera; he did not, indeed, 

 see the actual opening between the antheridium and asco- 

 gonium, but the nuclei in the female cell doubled in numbers 

 as the male cell became quite empty, and the nuclei thus con- 

 gregated fused in pairs before the ascogenous hyphae began to 

 grow out from the ascogonium. In some forms the female cell 

 alone is present. In one such, Humaria gramilata, V. H. Black- 

 man and H. Fraser have found that the large number of nuclei 

 in the ascogonium (upwards of a thousand) fuse in pairs. There 

 is here no question of a male organ, but the writers interpret 

 the fusion as a very reduced form of conjugation. Gustav 

 Ramlow describes the ascogonium in Thelebolus stercoreus, a 

 minute ascomycete with only one ascus. There is no fusion 

 between the ascogonium and any other cell, and no fusion be- 

 tween nuclei until the ascus is formed. It would almost seem 

 as if the ascomycetes would need to be examined species by 

 species, as no two appear to behave exactly alike. 



A great deal of attention has been directed to the develop- 

 ment of the ascus, a branch of investigation which Harper also 

 started afresh. The most recent paper on this point is by 

 H. Faull, who examined and compared a large number of 

 species. He finds that the asci bud out from the penultimate 

 cell of the ascogenous hyphae only in some cases. In a few of 

 the species examined they arose from the terminal cell, in others 

 they grew apparently from any of the cells. In every case 

 definitely determined by him, and by previous workers, there 

 were two nuclei present in the young ascus which fused, and, 

 after a resting stage, divided to form the ascospores. Harper 

 held that the astral rays which radiate from the poles of the 

 nucleus coalesced and bent round the nucleus to form the spore- 

 membrane. Faull sees no evidence for this : the spore wall, he 

 contends, is formed from the cytoplasm of the ascus independ- 

 ently of these rays. This view would certainly show less of 

 dissimilarity between the spore of the ascus and the spore of the 

 various sporangia of the lower groups, and so Faull comes to 

 the general conclusion that the phenomena of spore-formation, 



