MOLDS 47 



In molds are found still other reserve products. One often sees 

 globules of fat in the cytoplasm, which are easily stained by a black- 

 brown by osmic acid; and glycogen which can be differentiated by iodine 

 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. 



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 species found under the same conditions frequently 

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

 collectively to these organisms, though no sharp limits 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 

 constantly found upon every kind of putrescible matter, especially as 

 the causes of fermentation or decay in food. Their spores (conidia) are 

 produced in countless numbers, and are so light that they float in air 

 currents and are carried by contact in every conceivable manner by 

 animals and by man. The life cycle from spore to spore is frequently 

 very short, often being completed in twenty-four hours or less. Many 

 of these forms are propagated for an indefinite number of generations by 

 asexual spores or conidia but produce sexual fruit when special conditions 

 are furnished. Some of them have never been induced to develop a 



* Prepared by Charles Thorn. 



