14 COMPARATIVE MORPHOLOGY OF FUNGI 



1. Amphimixis, the copulation of two sexual cells not closely related. 



A. Merogamy. Specific gametes which have arisen as daughter cells of 



gametangia and serve as sexual cells (e.g., Syjichytrium, Fig. 11). 



B. Gametangial copulation. Where the differentiation of gametes is 



suppressed {e.g., Phytophthora, Fig. 51). 



C. Hologamy. A special case of gametangial copulation, in holocarpic 



forms where the whole thallus is transformed into a gametangium 

 and copulation takes place between two mature individuals (e.g., 

 Polyphagus, Fig. 26). 



2. Automixis. Self-fertilization following copulation of two closely related 

 sexual cells or sexual nuclei. 



A. Parthenogamy. Copulation between two cells of the female sexual 



organ (e.g., Ascobolus citrinus, Fig. 227). 



B. Autogamy. Fusion of nuclei in pairs within a single cell of the 



female sexual organ, not accompanied by cell fusion (e.g., Humana 

 granulata, Fig. 229). 



3. Pseudomixis. Copulation between two vegetative cells. 



A. Pseudogamy. Between cells not closely related to each other 



(e.g., Peniophora Sambuci, Fig. 266, 1). 



B. Pedogamy. Pseudomictic copulation between mature and imma- 



ture cells (e.g., various yeasts). 



C. Adelphogamy. Pseudomictic copulation of mother and daughter 



cells (e.g., Zygosaccharomyces Chevalieri, Fig. 93, 17 to 23). 



4. Apomixis. Vegetative development of sexual cells in the absence of 

 copulation. 



A. Parthenogenesis. Apomictic development of haploid cells. 



B. Apogamy. Apomictic development of diploid cells. 



Besides the complication that the original processes of fertilization 

 are replaced in the course of development by all sorts of substitutes, in 

 the study of fungi there is another difficulty. The diagram of a life cycle, 

 (p. 1) which at the instant of fertilization shows a complete transition 

 from the haploid to the diploid phase, describes only the exceptional case 

 in fungi. In the lower fungi, there is simple fertilization where a fusion of 

 two sexual cells (plasmogamy) is followed normally and directly by a 

 fusion of both haploid nuclei into a diploid zygote nucleus, a syncaryon 

 (caryogamy) ; in most fungi, however, caryogamy is delayed and is only 

 completed when the necessity for meiosis appears. Thus the sexual 

 nuclei unite only to form a dicaryon in which the paired nuclei pass 

 through their further development synchronously (conjugately); and in 

 this condition possess the same ability to activate the somatic develop- 

 ment as after complete caryogamy, although the nuclei remain spatially 

 separate. Their relation corresponds to that of Cyclops in which the 

 parent chromosomes remain separate up to the time of egg formation 

 (synapsis!). But in the case of Cyclops they are surrounded by the same 



