292 YEASTS AND YEAST-LIKE FUNGI 



Candidoideae. We have seen that many diverse types of fungi 

 may at times assume a unicellular form, frequently the single cells 

 being hardly distinguishable from yeasts. Since these forms also 

 produce other well-defined reproductive bodies, there is little ques- 

 tion concerning their classification. But there exists quite a group 

 of fungi which produce at times mycelium, at times free yeast-like 

 cells, which do not form conidia or other bodies serving to identify 

 them, or which may produce conidia that grade so imperceptibly into 

 the free yeast-like cells that it is frequently difficult to tell which is 

 which. Yeast-like cells are formed so regularly and comprise so 

 prominent a part of the microscopic picture that, in spite of their 

 non-specific characters, they are given considerable attention in 

 classification. Such forms are looked upon as being transitional be- 

 tween the molds and the yeasts proper. Because they are transi- 

 tional types, we find a great deal of confusion and contradiction 

 regarding their proper nomenclature and classification. The same 

 organism has been placed in half a dozen different genera depending 

 upon the interpretation given by this author or that to the yeast-like 

 cells. We must include in this transitional group a very heterogenous 

 mixture of fungi whose true systematic relationships are obscure. 

 "Transitions may be troublesome in taxonomy, but they are a part 

 of Nature and we have to classify them." (Diddens and Lodder.) 



The microorganisms to be considered have been mostly referred to 

 as the genera Oidium, Monilia, or Mycoderma although many other 

 generic names have been used. These three generic names are them- 

 selves used in different senses. As we have seen Mycoderma is used 

 to mean (1) film-forming asporogenous yeasts, the apparently cor- 

 rect usage, (2) acetic acid bacteria, and (3) certain yeast-like fungi. 

 Oidium and Monilia have been used in many different senses also 

 and various authors have used different and mutually contradictory 

 methods for differentiating these genera. Castellani differentiates 

 Moniha from Oidium on the basis of production of gas from glucose, 

 Stevens on the lack of ability to invade tissues of plants. Oilman and 

 Abbott on the branching of conidiophores, and Henrici on the basis 

 of blastospore as opposed to arthrospore production. Too often 

 phytopathologists have been unaware of the medical mycological 

 literature and as often medical mycologists have ignored rules of 

 nomenclature and general mycological literature. Hence the same 

 organism has frequently been designated by eight, ten, or more 

 generic names. Recently, efforts of Ciferri and Redaelli,^ Langeron 

 and Talice,^ Diddens and Lodder,^ and others have begun to con- 

 struct some order out of a virtual chaos and soon we may hope to 



