INTRODUCTION. 273 



comprehension of our subjoined resume of the division of the 

 Saccharomycetaceai into genera in accordance with the principles 

 established by HANSEN (XLIX.) in 1904. Previous to his 

 researches on the fungi in question, nothing had been done 

 beyond the establishment of the Saccharomycetes as a separate 

 genus, the division into species being of an unreliable nature ; and 

 Hansen was the first to place these investigations on an experi- 

 mental basis. Examination of the various species discovered in 

 the course of years then revealed the desirability and possibility of 

 elevating the existing genus Saccharomyces to the dignity of a 

 family (Saccharomycetacea'] t which Hansen divided into eight 

 genera. In the case of two of these, viz., Monosporas&d Ntmato- 

 spora, which are briefly described in 280, some doubt exists as to 

 whether they really belong to the Saccharomy cetacean The remain- 

 ing six genera, which, on the other hand, are recognised as true 

 Saccharomycetacece, can be separated into two main groups. 



The first principal group differs from the second, inasmuch as 

 sowings in nutrient liquids furnish sedimental yeast exclusively 

 at the outset, the production of films occurring only at a much 

 later period, if at all. The film is more or less strongly mucinous, 

 the only exception being Saccharomyces capsularius, which gives a 

 film resembling that of Oidium. It is probable that more accurate 

 observation will reveal the presence of isolated islands of yeast 

 (see pp. 1 2 o, 121, vol . ii .), even in those species at present considered 

 to lack the power of producing films. The endospores of the 

 species belonging to this first group are globular, oval or reniform, 

 smooth and provided with one or two membranes. The spores 

 germinate either by gemmation or the production of a proinycelium. 

 The great majority of the species incite alcoholic fermentation. 

 Hansen divides this group into four genera, one being the newly 

 defined genus Saccharomyces, described in 278, whilst the other 

 three are called Zyyosaccharomyces, Saccharomy codes, and Saccha.ro- 

 mycopsis, and are dealt with in 279. It need only be mentioned 

 that the genus Saccharomycodes was established for the organism 

 previously known as Saccharomyces Ludwigii, and a similar species 

 described by Behrens. In its new form, Hansen's genus Saccharo- 

 myces comprises a large number of species, and is divided into six 

 sub-groups based on the behaviour of the species towards sugars. 

 The hitherto imperfectly characterised genera Hansenia and 

 Torulaspora are referred to briefly at the end of 278. The 

 nomenclature of the species included in the newly defined species 

 Saccharomyces has been altered considerably, a number of names, 

 hitherto current in Mycology and also used in nearly all the 

 previous chapters of the present work, having been replaced by new 

 ones. Thus, for example, the organism previously known as Sacch. 

 cerevisiie /., Hansen, is shortened in the new classification to 

 Sacch. cerevisi(t j ; Sacch. Pastorianus I. becomes Sacch. Pastorianus ; 

 Sacch. Pastorianus III. is changed to Sacch. validus, and so on. 



