684 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Spore-development in Aphanomyces.*— Rothert confirms De Bary's 

 work on Aphanomyces, and adds further observations. He describes the 

 formation of the sporangia and the spores : the latter characterised by a 

 circular massing of the plasma, which takes at the same time a foam- 

 like formation. When the spores are fully formed, there remains a 

 plasma thread forming a bridge between them. The connection 

 accounts for the grouping of the non-motile spores after leaving the 

 sporangium. 



Sexual Reproduction in the Mucorinege.f— A. F. Blakeslee presents 

 us with the extended paper, a summary of which has already appeared. 

 In a long introduction he discusses the points of interest in connexion 

 with the formation of zygospores. He finds that the conjugating gametes 

 do not grow towards each other, but are the ends of branches in close 

 contact, and that as they swell and grow, they push apart the supporting 

 hyphas. He explains the distinction between homothallic or bisexual 

 and heterothallic or unisexual strains, and gives an historical review of the 

 many theories held by workers as to the causes inducing the formation 

 of zygospores in this group of fungi. An account is also given of all 

 the species in which zygospores have been recorded. He finds that 

 there are two main groups of Mucorineae, homothallic and heterothallic, 

 the latter largely outnumbering the former. In the heterothallic group 

 zygospores are only formed between the hyphae of different plants or 

 " strains." Given these two strains, the other conditions of nutrition 

 and moisture are unimportant, except that where the substratum is too 

 dry no fusion takes place. Moisture, he finds, though not a determining 

 factor, has a decided influence on zygospore formation. The stimulus 

 to the formation of progametes becomes operative through the osmotic 

 activity of the hyphal contents ; and if the surfaces of the two membranes 

 are dry, there will be no osmotic influence between the fluids contained 

 in them. The author records several instances of successful hybridisa- 

 tion between different species, but always between the ( + ) strain of one 

 and the ( — ) of another. Mature zygospores are not formed, however ; 

 the process goes no further than the formation, or the cutting off, of the 

 two gametes. A complete bibliography of the subject is appended. 



Development of Mucorini4— J. Dauphin has tested the influence of 

 various carbohydrates on the growth of Morierellapolycephala. He finds 

 that glucose, levulose, and galactose favour the appearance of sporangia 

 and induce the formation of zygospores hitherto unknown in this fungus. 

 Lactose and saccharose give only sporangia and chlamydospores ; with 

 maltose and mannite chlamydospores alone are produced. The author 

 considers that he has gained some knowledge of the conditions favour- 

 able to the formation of zygospores, a subject which is still enveloped in 

 obscurity. 



Conidial Form of Morchella esculenta.§— Marin Molliard produced a 

 conidial growth from the ascospores of Morchella, and he finds it identical 



* Flora, xcii. (1903), pp. 293-301. See also Centralbl. Bakt., xii. (1904) p. 502. 

 t Proc. Amer. Acad. Arts and Sci., xl. (1904) pp. 205-319 (4 pis.). 

 t Comptes Rendus, cxxxix. (1904) pp. 482-4. 

 § Rev. Gen. Bot., xvi. (1904) pp. 209-18 (1 pi.). 



