5° 



MORPHOLOGY AND CULTURE OF MICROORGA^aSMS 



Thamnidium.— Of related genera, Thamnidium differs from Mucor 

 in the production of two kinds of sporangia. The terminal sporangium 

 of a fruiting hypha resembles that of Mucor; the secondary or accessory 

 sporangia which are borne upon side branches of the sporangiophores 

 are smaller, lack the columella, and produce few to several spores 

 within an outer wall. 



Fig. s2.—MiM;oHnea. Mucor, Rkizopus. A, B, C, D, Formation of the zygo- 

 spores from conjugating branches; E, section of D; F, mature zygospores in section; 

 G, germination of zygospores; H, diagram of fruiting stolons of Rkizopus nigricans; 

 K, section of sporangium during spore formation, highly magnified (From Tahula 

 Botanical.) (Reduced one-half.) (By permission of A. F. Blaskeslee.) 



Thamnidium elegans, Link, produces primary and secondary spor- 

 angia on different hyphse, together making white colonies. The fertile 

 side branches are produced in whorls and bear whorls of branchlets 

 from their centers which in turn produce sporangioles from the tips of 

 short straight twigs or branchlets. 



Penicillium. — -The extremely abundant green molds most fre- 

 quently belong to the genus Penicillium, although some members of 

 other groups may be confused with them at times. 



Characters. — Colonies are composed of loosely woven hyphae, 

 branched, septate, colorless, or bright colored. The fertile hj^hse 



