Cultivation 



439 



mycelial threads into which these grow, and of chlamydospores and 

 conidia. 



The yeast-like elements measure 5 to 6 /i in length and 4 /i in 

 breadth. They have an oval form and cannot be distinguished from 

 yeast cells. The mycelia are formed by elongation of these elements, 

 some of which appear slightly elongate, some greatly elongate and 

 slender and more or less septate, like those of the true molds. They 

 are refractile, doubly contoured, and contain droplets, vacuoles, and 

 granules. In the interior of the hj^hae conidia-like organs often 

 appear, and chalmydospores are found. The latter are large, oval, 

 doubly contoured, highly refracting, and have been seen by Plaut 

 to germinate. 



The morphology is, however, extremely varied, and the greatest 

 differences of interpretation have been expressed regarding the dif- 

 ferent elements. 



Fig. 166. — Oidium. (KoUe and Wassermann.) 



Cultivation. — 'The organism grows readily in artificial media, both 

 with and without free access of oxygen. An acid reaction is most 

 appropriate. 



Colonies. — ^The superficial colonies upon gelatin plates are rounded, 

 waxy, and coarsely granular. The deep colonies are irregular in 

 shape and show feathery processes extending into the medium. The 

 color varies according to the composition of the medium, from snow 

 white on ordinary gelatin to meat-red on beet-root gelatin. A sour 

 odor is given off from the cultures. 



Gelatin Punctures. — Along the line of puncture there is a slow forma- 

 tion of rounded, feathery, colorless colonies, not unlike those shown 

 by many molds. The gelatin is slowly liquefied only when it con- 

 tains sugar. In such cultures chlamydospores are abundant. 



Agar-agar.— 'Cultmes are similar to those in gelatin. 



Bouillon.— 'The organism grows only at the bottom of the tube in 

 the form of yellowish-white flocculi. 



