CRYPTOGAMS 



399 



p 



A, yeast-cell ; B, C, 

 yeast - cell budding ; D, ascus with four spores. 

 (After GUILLIEUMOND, x 1125.) 



cells are abstricted. In the ginger -beer yeast (Zyyosacckuroinyccs} and in 



Schizosaccharomyces the yeast - cells conjugate by means of long tubes before 



spore - formation. These nuclear fusions possibly correspond to those in the 



young asci of other Ascomycetes. 



Physiologically these Fungi are remarkable for their power of exciting, by 



means of an enzyme (zymase), the 



fermentation of saccharine solutions, 



alcohol and carbon dioxide being 



produced. The beer yeast (tiacchci- 



romyces cerevisiae) is only known in 



the cultivated form ; the wine yeast 



(S. cllipsoideus), on the other hand, 



occurs regularly in the soil of vine- 

 yards in the spore-form ; the latter 



is therefore always present on the 



grapes and need not be added to the 



grape-juice. Other genera, in some of which a mycelium is developed, belong to 



this order. 



No evidence is at present forthcoming to show that the Yeasts are to be regarded 



as developmental forms of other 

 Fungi. In various members of the 

 Exoasci, and Ustilagineae, however, 

 yeast-like conidia which reproduce 

 by budding are known. Possibly 

 the Saccharomycetes are reduced 

 Ascomycetes, or they may represent 

 an independent group of very simple 

 Fungi. 



Order 7. Laboulbeniaceae ( ro ) 



Tlu; Laboulbeniaceae are a group 

 of minute Fungi occupying an iso- 

 lated position ; our knowledge of 

 them is largely due to the work 

 of TH AXTEU. Their thallus consists 

 of two to a number of cells, and 

 is attached to the body of the in- 

 sect, most commonly a beetle, on 

 which it is parasitic by means of 

 a pointed process of the lowest cell 

 inserted into the chitinous integu- 

 ment of the insect or by means of 

 rhizoids which penetrate moredeeply. 

 Fie. S&.-StignMtomyccs Jiaeri. Description in text. Utiyniatomijces Baeri which occurs 

 .4, spore ; B-F, sucees>i\v developmental stages. D. onhouse-fliesin Europe may be taken 

 with spermatia escaping from the antheridia are ; K, as an example. The bicellular spore 

 with antheridia above and the lateral female organ ; (pig> 342 ^ which has ft mucilagi . 



nous outer coat, becomes attached 

 by its lower end (B), and divisions 

 occur in both [cells (C). From the upper cell an appendage is developed bearing 



in- 



F, Perithecium with developing asei ; <1, ripe ascus. 

 (After THAXTER.) 



