SEXUAL ORGANS AND SEXUALITY 15 



nuclear membrane, while in the fungi they remain in their original nuclear 

 membranes. 



With this retardation of caryogamy, there goes a spatial separation. 

 The binucleate zygote continues its growth without completing the 

 fusion of nuclei and develops, in the higher fungi, to a new thallus whose 

 cells, virtually diploid, morphologically contain two sexually differenti- 

 ated haploid nuclei. This new phase, intruded between plasmogamy 

 and caryogamy, is called the binucleate phase. To distinguish it from 

 the usual diploid phase we will underline it in the life-cycle diagrams with 

 two thin instead of one heavy line. 



It is significant that in spite of this removal and retardation, caryog- 

 amy must take place in definite organs. The organs in which the ferti- 

 lization processes are completed and the dicaryon ends are called zeugites. 

 As caryogamy is delayed until the necessity for meiosis appears, these 

 zeugites function in most forms as gonotoconts. The diagram on page 1 

 might therefore be modified as follows: 



I ~P~ C R | 



Haploid thallus — >Sexual cells -^Diploid thallus— >Zeugites— >Gonotocont— >Tetracytes 



Diagram II. 



The two moments, the transformation of the cells which complete 

 the sexual act and the division of the sexual act itself into plasmogamy and 

 caryogamy, separated in time and space, so that reproduction is sepa- 

 rated in time and space from the sexual act which brings it about, are both 

 fundamental processes which, since the contributions of Bary and 

 Brefeld, have made possible a deeper interpretation of the classification 

 of fungi created by these two investigators. We shall give special 

 attention to these processes in the rest of the book. 



Classification. — Fungi are considered as thallophytes without chloro- 

 phyll. In this book, the bacteria and Myxomycetes are not considered. 

 From these two latter classes, the fungi in the narrower sense are distin- 

 guished by their diversity of fructifications, from the bacteria by the 

 possession of true nuclei and from the Myxomycetes, excluding groups 

 here considered under the Archimycetes, by the possession of cell walls 

 at all stages of development. In contrast to the Myxomycetes, the 

 other fungi are often called Eumycetes; in other terminology, however, 

 this name is reserved for the Ascomycetes and Basidiomycetes, to dis- 

 tinguish these two classes from the Phycomycetes. 



The classification of fungi rests upon the consideration of the life cycle 

 and the development which their thalli and organs of fructification have 

 attained in both portions of the life cycle. On this basis they may be 

 divided into four classes: Archimycetes, Phycomycetes, Ascomycetes and 

 Basidiomycetes. The Archimycetes and Phycomycetes are distinguished 

 by the primitive character of the thallus, naked in the Archimycetes, or 



