46 MORPHOLOGY AND CULTURE OF MICROORGANISMS 



in iodide of potassium. The glycogen is contained in either the 

 cytoplasm or the. vacuoles. It is generally very abundant. 



These products (fat and glycogen) undergo the same evolution as 

 the metachromatic corpuscles, and they also accumulate in the organs 

 of fructification (asci, conidial organs) to serve in the nourishment of 

 spores and conidia.. 



Fig. 30. — Formation of metachromatic corpuscles in a cell of the perithecium of 

 Peslularia vesiculosa. The rod-mitochondria form on their crossings vesicles (c) 

 consisting of a metachromatic corpuscle unstained by the special method which 

 served to differentiate the chondrium. Some corpuscles (o), more highly developed, 

 are found in the vacuoles still surrounded by their mitochondrial sheU; others (c) 

 at the completion of their , development have worn through their nutochon4rial 

 covering. 



Cell- Wall. — ^The cell-wall of molds is quite distinct and often 

 thick. It is sometimes cutinized. According to Mangin, it consists 

 of callose and pectose with which is often associated a kind of cellulose. 



Specific Consideration of Molds* 



A few species are found to grow very constantly in the same situa- 

 tions as bacteria. These are associated with forms of decay, fermenta- 

 tion, or disease, either as primary or secondary causes. They thus 

 become important to the bacteriologist who studies them by the same 

 methods as bacteria. These species belong to widely scattered groups 

 of fungi, so that spedes found under the same conditions frequently 

 difEer greatly in appearance. The common term, molds, is applied 

 collectively to these organisms, though no sharp hmits can be set to 

 the use of the term. Physiologically these species can be considered 

 in three series: 



Cosmopolitan Saprophytes. — Certain species are capable of 

 growing within very wide limits of temperature and of composition of 

 substrata. Many of these have accompanied man everywhere and are 



• Prepared by Charles Thom. 



