98 



COMPARATIVE MORPHOLOGY OF FUNGI 



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gemmae generally arise endogenously; multinucleate protoplasmic por- 

 tions of varying circumferences, draw together and, inside the original 

 hyphal membrane, surround themselves with a special thick wall. The 

 stipitate gemmae (mycelial conidia, stylospores) of Mortierella and Syn- 

 cephalis are cut off in scattered or racemose groups on short branches of 

 the mycelium (H. Bachmann, 1900). Under suitable conditions both gem- 

 mae and sclerotia develop to new mycelia. 



Asexual reproduction takes place through spor- 

 angia with sporangiospores. The parts of the 

 mycelium from which the sporangia develop swell 

 considerably and their nuclei divide repeatedly. 

 In forms with stolons, the sporangiophores branch 

 almost exclusively from the nodes (Fig. 55, 1) and 

 are then firmly attached to the substrate by the 

 group of rhizoids; but in Absidia they branch 

 directly from the stolons, midway between nodes. 

 In Mortierella Rostafinskii (Brefeld, 1881) the rhi- 

 zoids develop so luxuriantly that they surround 

 the lower quarter of the sporangiophore like a 

 thick sheath (Fig. 57); their outer wall is yellow 

 or brown and cuticularized so that the whole 

 structure looks like a capsule. 



In the lower species, the sporangiophores are 

 unb ranched; in the higher species, they are forked, 

 racemose, corymbose, cincinnal, etc. The tip of 

 each branch swells up to a sporangium, allowing 

 the protoplasm and nuclei of the swollen hyphal 

 portion to migrate into it, and is finally abjointed. 

 In the subfamily of the Mortierelleae, this septum 

 F IG- 57. — Mortierella is plane or slightly bent, like a watch glass; in the 

 Rostafinskii. Sporangio- Mucoreae, Piloboleae, etc., it is arched far into 



phore surrounded by hy- . 



phae, h, at base, t, in the sporangium (Fig. 54, 2 and 3). 1 his peculiar 

 sheath; a, end of stolon. d ome (columella) is generally smooth, cylindrical 



(X 100; after Brefeld.) \ ' t . ■. du 



or pynlorm and even after maturity oi the spor- 

 angium remains clinging to the stipe. In Pilobolus roridus (Tieghem, 

 1875) and Pilaira anomala (Brefeld, 1881), a sporiferous hypha swells 

 under the head into a large inflation on which the sporangium rests (Fig. 

 58, 1 and 2). On the absorption of more water, the sporo phore bursts 

 at the point of insertion of the columella and shoots out the sporangium 

 and columella, often to a height of 1 m. and more, with an audible sound. 

 The wall of the sporangium in different tribes varies in chemical 

 composition. In the Mucoreae the wall consists fundamentally of cellu- 

 lose, which is subsequently so much incrusted with calcium oxalate crys- 

 tals that it becomes fragile; simultaneously the cellulose is transformed 



