16 HARRY WARREN ANDERSON 



Generic Separation. In the preceding section it was stated that a distinct 

 morphologic difference exists between the forms which never produce new cells 

 by septation and those which may show septation under proper conditions. 

 This fundamental difference has been recognized by a number of writers. 

 Cao ('00), on the basis of the development of a villous growth in gelatin-stab 

 cultures and the formation of elongated cells, wished to place all such forms 

 in the genus Oidium. He described a large number of such fungi using num- 

 bers only to designate his 'species.' He did not distinguish between those 

 which form elongated cells without septation and those which produce septa. 

 t Will ('03-'08), in several instances in his articles on "Sprosspilze ohne Sporen- 

 bildung" called attention to these 2 types. Geiger ('10) also differentiates clearly 

 between the 3 groups enumerated. He believed that the forms having septate 

 hyphae should be placed in the genus Monilia on the ground that Monilia 

 Candida is of this type. He erects a new genus, Pseudomonilia, to include 4 

 species having elongated narrow cells of a hyphal nature, but without septa. 

 The forms producing septate mycelium under certain circumstances but usually 

 forming budding cells are included, by most authors, under either the genus 

 Monilia or Oidium. The latter genus is, as a rule, used to designate forms of 

 the Oidium lactis type. The species which do not form these elongated septate 

 hyphae are usually placed in the genus Torula if they do not form a pellicle 

 in liquid mediums, while if such is formed, they are called Mycoderma. 



It is recognized that ' there may occur conditions under which the non- 

 septate might pass over into the septate type. But a series of observations on 

 a number of forms which produce elongated cells but do not form septa tends 

 to show that the character is constant. 



We have, therefore, a group of the Fungi imperfecti which is distinguished 

 by the fact that, with the conditions under which they grow and under all 

 the usual conditions of laboratory culture, reproduce by budding exclusively 

 and do not form a dry, aerial mycelium. This group in turn may be separated 

 into 2 distinct morphologic groups on the basis of septation or nonseptation. 

 These 2 groups should be given generic rank and such a classification is to 

 be proposed. 



The formation of elongated, radiating, thread-like filaments in gelatin-stab 

 cultures does not prove that septate hyphae are formed. Hanging drop cul- 

 tures which are allowed to develop several days are most useful in showing 

 this character. The filaments extend from the drop, in the case of solid 

 mediums, into the water of condensation on the cover glass, and may be 

 examined even under an oil immersion objective. By watching these for an 

 hour or so the formation of septa may be observed if it occurs. Various 

 mediums may be used for hanging drop cultures but a most satisfactory one 

 is 0.5% beerwort agar solution. A tube containing such a solution is melted 

 and a few yeast cells on the end of a needle are introduced. The tube is 

 then shaken and a portion drawn up into a sterile glass tube with a fine drawn 

 end. The drops are then placed on a sterile cover glass and inverted on a 

 ring in the usual manner. 



The Basis of Specific Classification. The basis of specific differentiation in 

 most microscopic organisms, aside from the bacteria, is morphologic. In the 

 fungi the character of the mycelial growth, the form, size, marking, and 

 arrangement of the reproductive bodies, whether sexual or asexual, are used 

 for separating genera and species. When any of these characters vary within 

 the species, the limits of variation are not wide, and may be easily determined 

 by biometric methods. Frequently internal structures, thickness of spore walls, 



