154 BOTANICAL GAZETTE [august 



of HaberL-\xdt's "arm palisade parench)TTia," differing from it in the several 

 arms or branches being borne upon a larger basal cell. This peculiar modifica- 

 tion is called by the author "coralloid palisade parenchyma/' and is known only 

 in ^leliosma. The pneumatic tissue is often verj' open and passes insensibly 

 into the palisade tissue; and it appears as if the chlorenchmya might be com- 

 posed merely of pneumatic tissue modified somewhat on the upper face of the 

 leaf-blade. Calcium oxalate occurs in all the species of Meliosma, and mostly as 

 druids; globose conglomerations, however, w^ere also observed in some few 

 species. — Theo. HoLii. 



Origin of the yeasts. — The problem of the autonomy of the group of Saccharo- 

 myces has been reopened by the researches of Viala and Pacottet.^ In two 

 ascomycetes, Gloeosporium ampelophagitm, the anthracnose of the grape, and 

 G. neruiseqiium, the anthracnose of the plane-tree, they have found a complex 

 polymorphism, the most striking feature of which is the presence of conidia 

 capable of budding in yeast-like fashion and of forming endospores in cysts, 

 hke yeasts, but w^hich are produced from the true ascomycete mycelium. Other 

 fungi, such as the ^Mucorineae, Ustilagineae, etc., bud in this fashion also, but 

 the formation of endospores was regarded by Hansen as a certain characteristic 

 of true yeasts. If these observations of Viala and Pacottet are correct, they 

 would seem to indicate that what are known as yeasts may only be forms of 

 polymorphic ascomycetes. 



GuiLLiERMOND,^ in reviewing this work, grants that there may be such forms, 

 but strongly suspects that the cultures were impure and contained not only the 

 Gloeosporium but also a yeast living with it. The most experienced observers 

 have been led into errors from this same cause. In defense of the autonomy of the 

 Saccharomycetes and at the same time of the interpretation of the cyst producing 

 endospores as an ascus, Guiluermond'^ gives a general review of the yeast 

 situation. The extended work of Hansen and his students has made it highly 

 improbable that our industrial yeasts could ever revert to the mycelial condition, 

 that is, their characters have become so fixed that now they form an independent 

 and distinct group of the ascomycetes. The conjugations in such yeasts as 

 Zygosaccharomyces Barkeri and Schizosaccharomyces odosporus, as they have been 

 observed by Barker^^ and Guilliermond, is the strongest reason for consider- 

 ing the resulting product as an ascus. This conjugation, with its fusion of nuclei 

 and subsequent division into endospores, is regarded by Guilliermond as the 

 equivalent of the fusion of the two nuclei in the ascus and the formation of asco- 

 spores. It is true that a majority of the yeasts do not show this conjugation, but 



s Viala et Pacottet, Compt. Rend. Acad. Sci. Paris 142:458-461. 1906. 



9 Guilliermond, A., A propos de Torigine des le\^res. Ann. Mycol. 5:49-69 



1907. 



10 Guilliermond, A., Rev. Gen. Bot. 17^337-376 pis 6-g 1905. 



" Barker, Phil. Trans. Roy. Soc. London B. 194:467-485. pi. 46. 1901 



