546 \ BOTANICAL GAZETTE [December 



enlarges and forms the zygote or zygospore. The zygospore becomes sur- 

 rounded by a thick wall showing differentiation into several layers. In its 

 completed state it is inclosed in a network of hyphae whose walls fuse and 

 become greatly thickened, forming, in cross-section, a sort of a corona around 

 the zygospore. The nuclei were not observed to fuse in the zygospore of this 

 species, but in Endogone Ludwigii a single large nucleus, supposed to be a fusion 

 nucleus, was observed in some of the zygospores. This process of zygospore 

 formation was observed only in the two species mentioned. In the other 

 species the fruit body is filled with asexually formed chlamydospores or with 

 sporangia in place of zygospores. 



In his discussion the author points out the close resemblance between the 

 sexual reproduction of Endogone and the mucors on the one hand, and on the 

 other hand certain homologies between Endogone and the Ascomycetes. Thus 

 in the peculiar outgrowth of the fusion cell and the paired nuclei, he sees a 

 homologue of the ascogenous hyphae of the Ascomycetes, in some of which (as 

 Claussen has shown for Pyronema conjluens) the male and female nuclei do not 

 fuse, but remain in pairs until the formation of the ascus. — H. Hasselbring. 



Position of Gnetales. — In 191 1 Lignier and Tison published a brief 

 statement of their view that Gnetales are apetalous angiosperms, a statement 

 that was noted and commented upon in this journal. 13 Now they have begun 

 the publication of an extended argument for their position, the first part 

 dealing with Welwitschia. 1 * A very full resume of the literature prepares the 

 way for a consideration of all the kinds of testimony available. The conclu- 

 sions reached cannot be attacked on the basis of insufficient knowledge of the 

 facts at hand, but of course they rest upon personal judgment as to the relative 

 importance of the testimony, as do all conclusions in reference to phylogeny. 



The general contention in reference to Welwitschia is that the two kinds 

 of strobili ("inflorescences") have identical organization; that in the axil of 

 each bract there occurs a flower of the angiosperm type, comprising five cycles 

 of members; that the two innermost cycles form a tetracarpellary closed ovary 

 prolonged into a long style; that the functionally monosporangiate flowers are 

 obviousW derived from more primitive bisporangiate flowers; that Welwitschia 

 has retamed a large number of gymnosperm characters, especially in its 

 "anatom}%nd histology"; that in evolution such recondite characters change 



least rapidly, and therefore the phylogenetic position is to be determined by 

 the floral characters, which are essentially angiospermous ; that the great 

 reduction of flowers and their aggregation into inflorescences do not suggest 

 angiosperms in general, but rather a very specialized lateral phylum ; that the 

 method of specialization resembles that of the Anientales, and therefore Wei- 



« Bot. Gaz. 51:479. 1911- 



x * Lignier, 0., et Tison, A., Les Gnetales, leurs fleurs et leur position syste- 

 matique. Ann. Sci. Nat. Bot. IX. 16:55-185. figs. 40. 191 2. 





