ALGAL AND FUNGAL PROTISTS 47 



Gemmae. Spores of Mucor Mucedo sown on glucose 

 solution with free access of air produce the usual non-septate 

 mycelium, and oxygen is absorbed ; but if the growth is 

 submerged or air is replaced by hydrogen, the hyphae 

 become septate and break up into segments, which multiply 

 by budding, like yeast, to form a scum of large cells or 

 gemmae. This condition is easily produced in M . racemosus. 

 Alcoholic fermentation is caused by mucors in this state. 

 Spores placed directly in glucose solution free from oxygen 

 produce gemmae instead of hyphae. If air is admitted, 

 gemmae produce ordinary mycelium. 



Sporidia grown from promycelia of some species of 

 Ustilago multiply in a similar yeast-like way in nutritive 

 media such as manure heaps (Massee). Gemmae were seen 

 by Butler in PytJiium rostratum. A different sort of element 

 is also termed a gemma : it is found in old badly-nourished 

 mucors, and it is produced by a segment of mycelium being 

 isolated by septa. Such elements are really a sort of conidia. 



Parasitic Mucors. One of the parasitic Mucors is 

 illustrated in Fig. 10. Piptocephalis has for its host a Mucor 

 of another species. Its haustoria are seen as blunt projec- 

 tions provided with very fine branches which lose themselves 

 in the plasm of the host. 



Nuclei of Mucor. The tip of a hypha of Sporodinia 

 Grandis is shown in Fig. 11, a. Its point consists of proto- 

 plasm without either nuclei or cell- wall. In the rest of the 

 hypha nuclei are numerous especially near the point, where 



