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MEDICAL MYCOLOGY 



cases paired nuclei have been seen in the young asci. These thiek-walled asci 

 winter in the host. In spring, the outer layers of the ascus wall rupture and 

 the inner wall swells out as a cylindric or spherical sac (Fig. 28, 2). The 

 vacuoles fuse to a large central vacuole and the protoplasm lines the wall as 

 a homogeneous layer (Fig. 28, 3). Probably nuclear divisions take place in 

 it. By radial fissures, the wall layer is divided into uninucleate portions 

 (spore mother cells) which, after two simultaneous divisions separate into 

 four spores each (Fig. 28, 4-7). At the top of the sporangium, these gradually 

 form a ball which is forcibly ejected a short distance (Fig. 28, 8-10). 



Fig-. 28. — Protomyces maa-osponis. 1-6, germination of liypnospores ; 7-11, development 

 of ascospores ; 12, 13, copulation and developm-ent of ascospores, young- hypha with hypnospores. 

 (1-6, 11, IS X300 ; 7-10 XLSOO; 12 X660 ; U Xl70.) (After Biiren 1915.) 



The spores are ellipsoid, hyaline, and uninucleate. Directly after they 

 are ejected from the sporangium, they are connected by small processes and 

 copulate (Fig. 28, 11, 12). The nuclei enter the copulation bridge, but whether 

 they fuse or merely join in pairs to form a dicaryon is not yet ascertained, on 

 account of great difficulties in technic. In nutrient solutions they form pseudo- 

 mycelia only. When the spores reach a new host, they penetrate between the 

 epidermal cells and produce a normal mycelium. In Protomyces inundatus, on 

 celery, during the summer, the young asci may germinate directly without going 

 through the resting stage, but here the ascus wall is not thickened, and there is 



