42 MORPHOLOGY AND CULTURE OF MICROORGANISMS 



functions as true cells. It consists of compartments containing a 

 variable number of nuclei called coenocytes (Fig. 25, i). Each compart- 

 ment may be considered, not as a true cell, but as a colony of rudi- 

 mentary cells, energids. 



3. Still other molds have a mycelium consisting of true cells with 

 a single nucleus, as for example En domyces fibuliger (Fig. 25, 3 and 4) 

 and Endomyces decipiens. 



There are, moreover, molds which show both these last two struc- 

 tural types, with transitional forms between the two. For instance, 

 in Endomyces magnusii, the mycelium, ordinarily consisting of areas, 

 each containing many energids, can in some parts progress to a 

 uninuclear cellular structure. 



The conidia or spores of many molds may have either one or 

 many nuclei, according to the species. The spores of the Mucorinea, 

 for example, always have many nuclei (Fig. 24, 3); on the contrary, 

 the ascospores of the Ascomycetes, the conidia of Penicillium and 

 Aspergillus, contain generally but a single nucleus. 



The yeast forms which result from the budding of the mycelium in 

 some molds, most frequently have a single nucleus (Fig. 24, 4) ; how- 

 ever, in some, Dematium, are sometimes found yeast-forms containing 

 several nuclei. The yeast-forms of the Mucorinece, which are not other- 

 wise very typical forms, are always multinuclear. 



To whichever of these three structural forms a mold belongs, it 

 always represents some similar constitutional elements which we will 

 now consider. 



CYTOPLASM.- -The cytoplasm is a semi-fluid mass, somewhat dense, 

 sometimes homogeneous and containing a more or less considerable 

 number of vacuoles. Certain methods of fixing and staining have 

 recently made possible a demonstration, in the cytoplasm of the 

 most diverse molds, of the presence of a chondrium, very clear and 

 always splendidly exhibited. This consists mostly of fine rod- 

 mitochondria, very long and flexible, generally lying parallel with 

 the longitudinal axis of the cell (Fig. 26). Sometimes also it contains 

 granular mitochondria. 



The cytoplasm also has reserve products, of which we shall speak 

 later. 



NUCLEI. The nuclei show a differentiated structure which is 

 sometimes difficult to demonstrate. They consist of a nuclear 



