ZOOLOGY AND BOTANY, MICROSCOPY. ETC. 281 



Conjugation of Mucorini.* — M. P. Vuillemin describes a peculiar 

 mode of conjugation, or, as he prefers to term it, anastomosis, in a hitherto 

 undescribed species of Mucor, which he calls M. Jieterogamus. This process, 

 which results in the production of the zygospore, consists, in this species, 

 of the union of two very unequal elements proceeding from branches as dis- 

 similar as possible. The first stage is the appearance of a transverse septum 

 near the apex of the principal filament or of one of its branches. The apical 

 segment thus formed increases rapidly in length, but remains slender, and 

 contains a comparatively small amount of protoplasm. Below it the 

 protoplasm accumulates, and forms a lateral bud. The extremity of this 

 protuberance swells and curves, while opposite to this swelling the slender 

 filament puts out a lateral emergence. These two gametes, very unequal 

 in size, conjugate, and each becomes separated from its parent filament by 

 a septum ; the membrane which divides them disappears, as also does the 

 beak which constitutes the smaller gamete. 



The zygospore thus formed, has, when mature, a thin internal membrane 

 furnished with simple points, and an external brown coat with black almost 

 confluent plates. Instead of the single lateral swelling, there are some- 

 times two, which conjugate with the small protuberances from the single 

 slender filament. 



Membrane of the Zygospores of Mucorini.f — M. P. Vuillemin has 

 traced the history of development of the wall of the zygospores in Mucor 

 heterogamus (vide supra), and in some other species of Mucorini. He does 

 not admit two distinct membranes of different origin, as in the oosphere of 

 Peronosporese, but only one, with centripetal growth, which becomes 

 ultimately differentiated into five distinct zones. "While admitting that 

 these two organs are possibly of similar origin, he regards the zygospore of 

 the Mucorini as probably not of a sexual nature, but as an asexual spore 

 preceded in its formation by the simple anastomosing of vegetative 

 branches. 



Development of Pyrenomycetes.J — Herr F. von Tavel has followed 

 the history of development of some of the numerous kinds of parasitic 

 fungi found on plane-leaves. 



Of Gloeosporium nervisequum Sacc, which is very destructive to young 

 trees, he was unable to discover either the perithecia or pycnidia ; from 

 the gonidia was developed only a similar conidial form. 



Discula Plafani Sacc. must be regarded, from its history of develop- 

 ment, as a pycnidium, although differing in some points from the usual 

 structure. Its further development, however, the author was unable to 

 follow. Leaves of the plane-tree were infected by it without result. It 

 is always found in close proximity to the Gloeosporium, and may possibly 

 be a stage in its cycle of development. 



Growing out from a Cytispora was a new form, which v. Tavel describes 

 as Fenestella Platani. The basidia are unbranched, and produce enormous 

 numbers of unicellular spores. The asci contain eight spores, which are 

 septated, when mature, by three septa. Agreeing in general characters 

 with the genus Fenestella, it differs from the species hitherto known in the 

 small number of septa to the spores, and in the unusual development of 

 the neck. From its ascopores is developed a conidiiferous mycelium 

 belonging to the form Acrostalagmus. A genetic connection between this 

 and the pycnidial form, though probable, the author was unable actually 

 to determine. 



* Bull. Soc. Bot. France, viii. fl886) pp. 236-8. t Ibid., pp. 330-i. 



X Bot. Ztg., xliv. (1886) pp. 82.5-33, 841-6, 857-67, 873-8 (1 pi.). 

 1887. U 



