ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 471 



Fungi. 



(By A. Loerain Smith, F.L.S.) 



Study of Mucorini.* — A. F. Blakeslee continues his researches on 

 the Mucorini, and his recent paper deals with the germination of the 

 zygospore. His aim was to find at what stage the sexual character of 

 the thallus was determined. In a species like Sporodinia grandis, which 

 is homothallic, the germination of the zygospores is also homothallic. 

 In Mucor Mucedo, which is heterothallic, all the spores in a given spor- 

 angium produced from one zygospore are of the same strain, either (+) 

 or ( — ), so that segregation of sex is completed before the sporangium 

 is formed. In another heterothallic form, Phycomyces, the differentiation 

 of the spores in any sporangium is only partial. In addition to (+) and 

 ( — ) heterothallic spores, other spores are formed in this species which 

 produce homothallic mycelia. The latter has a peculiarly velvety 

 appearance owing to the presence of coiled and contorted outgrowths, 

 which the writer terms pseudophores ; sporangia are rarely formed, and 

 only on the comparatively stout and less coiled outgrowths. Zygospores 

 are also occasionally formed on the same mycelium ; usually they are 

 only partially developed. It has not yet been determined if this homo- 

 thallic nature is fixed. If the mycelium is transplanted from this 

 homothallic strain the character is retained, but spores from the 

 sporangia are again either (+) or ( — ). In nature the homothallic 

 mycelium is probably rare, and disappears in the course of a few 

 sporangial generations. 



Development of Thelebolus stercoreus.| — Gustav Ramlow has 

 worked out this minute Ascomycete. He gives first of all an account of 

 the researches and results of other workers on the same plant, and then 

 describes the methods he employed and the stains he used. The most 

 successful cultures were on agar with dung decoction. The first 

 beginnings of fruit formation show coiled hyphse like a screw which 

 grows up from the vegetative mycelium. Septa only appear in the coil 

 when the ascogonium has reached a considerable size and the enveloping 

 hyphse have begun to grow round it. These last arise from the stalk 

 hypha near the ascogonium. No communication is ever seen between 

 the ascogonium and any other hypha ; no fusion of cells takes place. 

 One of the ascogonium cells grows more vigorously than the others, 

 and the neighbouring cells also increase to a less extent. The cell 

 that has thus grown to so great a size is the young ascus. When 

 more than one ascus appears in the mature fructification there is, as 

 Brefeld showed, really a compound fruit formed, the result of two (or 

 more) ascogonia which have developed in close proximity. The 

 development of the large ascus is aided by the nutritive material stored 

 in the neighbouring cells which are rich in contents. 



The cytology of Thelebolus was also carefully worked out by the 

 author. Each vegetative cell is uninucleate : further details of these 

 nuclei were not noted. Before the septa are formed in the young 



* Ann. Mycol., iv. (1906) pp. 1-28 (1 pi.), 

 t Bot. Zeit., lxiv. (1906) pp. 85-99 (1 pi.). 



