XIII.] MOULDS. 425 



fortnight. Sometimes, however, the fluid will overrun with 

 Bacteria, to the exclusion of everything else. And very 

 frequently other moulds, such as Eurotium, or Mucor, 

 may appear instead of or along with Penicillium. 



1. Naked-eye characters. Note the powdery-looking 

 upper surface, white in young specimens, pale 

 greenish in older, and later still becoming dark sage- 

 green : the smooth pale under surface : the dense 

 tough character of the mycelium. 



2. Histological Structure. 



a. The mycelium. 



a. Tease a bit out in water, and examine first with 

 low, and then with a high power : it is chiefly 

 made up of interlaced threads or tubes — the 



a. Hypha. Note their diameter (measure) — 

 form — subdivisions (cells) — mode of branch- 

 ing — and structure : the external homogeneous 

 cell-wall; the granular less transparent proto- 

 plasm ; the small round vacuoles, the nuclei 

 (only to be seen on treatment with alcohol, and 

 staining with hsematoxylin). Draw. 



/?. The intermixed " Torulce." Note their size and 

 number. 



b. Hold a bit of the mycelium between two pieces 

 of carrot, and cut a thin vertical section with a 

 sharp razor: mount in water and examine with 

 low and high power. 



b. The submerged hyphae. 



Small branched threads hanging down from the under 

 surface of the mycelium: repeat the observations 

 2. a. a. a. 



