SEXUAL ORGANS AND SEXUALITY 13 



In the higher Ascomycetes, for reasons still unknown, the fundaments 

 of the antheridium are gradually reduced; thereby cross-fertilization 

 generally ceases and is replaced by self-fertilization, i.e., sl new group of 

 deuterogamous processes between daughter cells of the same mother cell 

 or between the nuclei of the same cell which are included in the term 

 automixis. 



Automixis is represented in the fungi by two forms: parthenogamy 

 and autogamy. Parthenogamy (parthenomixis of Winkler) is fertiliza- 

 tion which takes place between two female cells, i.e., in the fungi usually 

 between two cells of the archicarp (Fig. 227). In certain forms this 

 parthenogamic fusion of two specialized cells is suppressed and replaced 

 by pairing of nuclei within a single polyenergid cell of the archicarp 

 (Fig. 229). This automictic fertilization within a cell is called autogamy. 



From these forms in which the sexual organs (or in any case the 

 female organ) are apparently still typical in form, but no longer functional 

 and serving only as the site of automictic processes, there is a series of 

 intermediate stages to the other extreme in which the sexual organs are 

 entirely suppressed, the sexual processes occurring outside in the thallus 

 between any two sexually differentiated vegetative cells (Fig. 266, 1). 

 The latter process is called pseudomixis (pseudogamy of Hartmann). 

 Since the copulating cells are not morphologically distinguished from 

 other vegetative cells and since only the release of specific developmental 

 stimuli, which only appear later, marks this anastomosis of two vegeta- 

 tive cells as a sexual process, pseudogamy is often distinguished with 

 difficulty from the usual pseudosexual anastomoses which are brought 

 about by food relations. Its true character is only recognizable cytol- 

 ogically in the pairing of nuclei. If pseudogamy takes place between two 

 sprout cells (Fig. 301, 10 and 11), they are called gametes; in order to 

 avoid misunderstanding, this term should be reserved for merogamous 

 gametes. The ambiguous term pedogamy, often used in other senses, 

 may be used to indicate the pseudogamy between adult and young cells 

 (Fig. 93, 17 to 23). The special case of pseudogamy between mother and 

 daughter cell is called adelphogamy. 



Apomixis, the entire loss of fertilization, represents the last step in 

 this series of reduction of natural sexuality in which growth from repro- 

 ductive cells takes place vegetatively without cell or nuclear fusion or 

 any external stimulus of development. If the new individuals (in the 

 absence of fertilization) arise from haploid sexual cells, the process is 

 called parthenogenesis; if they arise (in the absence of meiosis) from 

 diploid sex cells, the process is called apogamy. 



For a better summary the different forms of fertilization are 

 tabulated, as far as they concern fungi, according to the scheme of 

 Hartmann : 



