212 SUMMARY OF CURRENT RESEARCHES RELATING TO 



fungus. It is always superficial, but damages tbe host-plant by ex- 

 cluding air and light. 



Morphology of Aspergillus herbariorum.* — H. C. L. Fraser and 

 H. S. Chambers have made a cytological study of the development of 

 this fungus. All the cells are multinucleate as well as the ascospores 

 and conidia ; the latter contain about four nuclei at maturity. The 

 archicarp arises as a narrow branch from the mycelium ; it is at first 

 aseptate, but cell-walls soon appear and cut off a septate stalk, a 

 unicellular trichogyne and a unicellular ascogonium. The antheridium 

 arises separately, and consists of a long stalk, at the apex of which is a 

 small antheridial cell. It either fuses with the tip of the trichogyne or 

 degenerates before reaching this stage. It seems probable that such 

 fusion sometimes takes place ; at other times it is replaced by the fusion 

 of ascogonial nuclei in pairs. The ascogonium then becomes septate, 

 and each cell produces ascogenous hyphffi, from which arise the asci in 

 which eight spores are formed. The authors suggest several new terms 

 to explain the different forms of nuclear fusion other than the normal 

 syngamy : viz. homoiogamy — a fusion of two sexual nuclei of the same 

 kind ; hylogamy — fusion of one sexual with one vegetative nucleus ; 

 and pseudogamy — fusion of two vegetative nuclei. In Aspergillus either 

 normal syngamy or homoiogamy takes place. A comparison is made 

 between Aspergillus and other Ascomycetes, and the relationship 

 of the group to the Uredineae and the red algae is indicated. 

 Aspergillus is regarded as a primitive ascomycetous type, from which 

 most others can be derived. 



Conidial Development of Xylaria Hypoxylon.f — F. Gueguen kept 

 this fungus in a moist chamber, and made observations on the forma- 

 tion of conidia, etc. He found that the stromata were positively 

 phototropic ; the elongation of the clubs and the production of conidia 

 took place only under the influence of light. The basidia produce at 

 their tips a large number of conidia, which do not germinate until they 

 have attained complete maturity. 



The region of growth of the " club " is subterminal a few milli- 

 metres below the tip ; the basidia that bear the conidia rise from 

 medullary hyphae. 



Remarkable Fungus Forms. — H. and P. SydowJ describe anew 

 species, Xylaria obesa, 15 cm. high and 10 cm. thick, which grew on 

 wood in Eastern Africa. The stroma is at first smooth and with a yellow 

 covering, the fruiting portion being distinguished by wrinkles and folds. 



T. Petch § publishes an account of a Sclerotium found in termite 

 nests, which had already been seen and described by Berkley as Sclero- 

 tium stipitatum. Petch was able to develop from these the ascus form 

 of Xglaria nigripes. When a comb from the nests is kept under a 

 bell-jar, it produces a conidial Xylaria. T. Petch concludes that this 

 fungus was continually kept in check by the ants as a weed. When 

 the nest is deserted in wet weather, Xylaria grows from the comb ; if 



* AnD Mycol., v. (1907) pp. 419-31 (2 pis.). 



t Bull. Soc. Mycol. France, xxiii. (1907) pp. 186-217 (2 pis.). 



% Ann. Mycol., v. (1907) p. 400. § Tom. cit., pp. 401-3. 



