FUNGI. ZYGOMYCETES. 



9 



organs of propagation, the mycelium not unfrequently produces the so-called gemmae 

 by the division of its tubular branches by tranverse septa into short members, which 

 round themselves off and can under favourable circumstances give rise to new mycelia. 

 In this way is explained the production of the so-called mucor-yeast by Mucor race- 

 mosus, the resemblance of which to true yeast is increased by the fact, that when 

 placed in an unfavourable nutrient solution it can multiply by sprouting. Mortierella 

 also produces similar gemmoid bodies. 



Under special circumstances the mycelium is able to attain the morphological 



FIG. 54. B mycelium (3 days old) of Phycomyces nitens grown in a drop of mucilage with a decoction 

 of plums ; the finest ramifications are omitted ; g the gonidiophores. A a gonidiophore of Mucor Mucedo in optical 

 longitudinal section. C a germinating zygospore s of Mucor Mucedo ; the germ-tube k puts out a lateral gonidio* . 

 phore^-. In D are conjugating branches b b, the extremities of which, a a, though they have not yet coalesced, 

 are already cut off by transverse walls ; the zygospore is formed from the coalescence of the cells a a. A, C. D 

 after Brefeld greatly magn., B from nature slightly magn. 



conclusion of its development by forming sexual organs ; thicker club-shaped branches 

 arise on adjacent branches of the mycelium which cross one another ; the -apical cells 

 meet and unite by the solution of their cell-walls at the point of contact (Figs. 54 and 

 55 Z), after a transverse septum has formed in each tube right and left of the point of 

 conjugation; the protoplasm aggregates in the chamber thus cut off and by considerable 

 growth of the whole separated chamber (Fig. 54 C)> or of its middle portion only (Fig. 55Z), 

 a comparatively large zygospore is formed, the thick outer wall of which is usually 

 dark-coloured and furnished with knobs or spike-like projections 1 . The zygospore 



[Bainier, Nouv. observ. sur les zygospores des Mucorinees (Ann. sc. Nat. 6 rae . ser. XIX).]. 



