ENDOMYCETALES 



139 



collects the cytoplasm with 2 or 3 nuclei. At the beginning' of copulation, it 

 bends over to meet the antheridium. In this stage, the swollen part contains 

 only one nucleus, the others having^ migrated (Fig-. 18, 5). The narrow an- 

 theridium contains, when young, 1-3 nuclei of which only one remains at the 

 tip. In about three-fourths of the cases, copulation occurs. The antheridium 

 approaches the ascogonium, swells slightly, and ab joints the apical uninucleate 

 gametangium from the stipe cell. Meanwhile the uninucleate tip of the 

 ascogonium is abjointed from its basal cell. Hereupon the walls separating 

 the gametangia dissolve, with the development of tlie zygote to a 4-spored 

 ascus (Fig. 18, 6-9). 



There often occur numerous variants of this usual course of development. 

 Thus, the antlieridium may approach the ascogonium at the side instead of 

 the tip; or both may be uninucleate without the abjnnction of basal cells; or 

 the ascogonium may develop parthenogenetically. 



Fig. 19. — Endomyces decipiens. 



1-3, stages of copulation; .'(-12, development of asci. (X 1,200.) 

 (After Juel 1921.) 



The end member of the heterogamous series is Endomyces decipiens, found 

 on fructifications of the mushroom, Armillario. mellea, producing its perfect 

 stage on the lamellae. Sexual organs are almost entirely absent, copulation 

 being heterogamous when present or very rarely isogamous (Fig. 19, 1-3). 

 The asci are lateral on the hyphae. Although sometimes three nuclear divi- 

 sions occur in the ascus, only 4 ascospores are formed (Fig*. 19, 4-12). In 

 cultures the hyphae easily break apart into uninucleate oidia. Sometimes the 

 tips of branches form thick-walled yellowish hypnospores instead of asci. 



The isogamous series begins with the genus Endomycopsis. In this genus 

 the abundant sprout mycelium is apparently connected with the adaptation 

 of these species to media containing starch and sugars. Wherever the sprout 

 cells arise on aerial mycelium, their diameter is smaller and the Avail some- 

 what thicker than in tlie submersed sprout cells. They are then ver}^ resistant 

 and survive a long period in temperatures up to 55° C. Biolog-ically their 

 significance seems to be that of hypnospores, and because of their exogenous 

 formation they are usually called conidia. 



