lO 



GENERAL MORPHOLOGY. 



mycelia constructed of short gemm^ ; whereas, when cultivated 

 on the surface of the liquid, and therefore in presence of abund- 

 ance of air, they form mycelia composed of elongated buds. 

 Further particulars of this will be found in § 246. 



The formation of mycelia composed of gemmae was first 

 observed in the case of yeast fungi, and was regarded as a 

 method of development peculiar to these organisms. Bail (I.), 

 however, in 1857, showed that this phenomenon also appears in 

 certain species of Mucor (see Chapter xliv.) when submerged in 



a 



/ B 





Fig. 98.— Torula. 



Specimen grown in beer wort, a, 

 represents a group of gemmating 

 cells, the condition of which, after the 

 lapse of an hour, is shown at h. Magn. 

 about 1000. {After Hansen.) 



Fig. 97.— Saccharomyces pyriformis Ward. 



Cell a, embedded in a hanging drop of gingerbeer gelatin and kept at a temperature 

 of 15° C. , threw out a bud (H) within 4^ hours. At the end of another 14 hours three 

 normal cells {y) were present, which grew to the aggregation S in another 10 hours. 

 This in turn had developed into the colony e in 13^ hours more. (Aftcr\M. Ward.) 



a nutrient solution containing sugar. For more precise ob- 

 servations of this phenomenon in the case of Mucors, we [are 

 indebted to Brefeld (XVI.). With Mucor racemosus, the 

 carbon dioxide collecting in the nutrient fluid acts upon the 

 cells, by which it has been produced, in such a manner that 

 the latter put forth none but spherical gemmae, and therefore 

 grow, not to a long and many-branched, unicellular mycelium, 

 but to one composed of stumpy gemmae. On the other hand, 

 Mucor mucedo treated in the same manner does not produce 

 similar gemmaj, though, according to Brefeld (XVI.), its spores, 

 when placed in a nutrient solution rich in citric acid, swell up 

 to large globules from whence proceed a number of similarly 



