XIII.] . MOULDS. 425 



fortnight. Sometimes, however, the fluid Avill 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 Penicilliiun. 



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 myceUum. 



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. Hyphce. Note their diameter (measure) — 

 form — subdivisions {cells) — mode of branch- 

 ing — and structure : the external homogeneous 

 sac; the granular less transparent protoplasm; 

 the small round vacuoles, the nuclei (only to be 

 seen on treatment with alcohol, and staining 

 with haematoxylin). Draw. 



/?. The intermixed " Toridce.'" 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 hyphse. 



Small branched threads hanging down from the under 

 surface of the mycelium: repeat the observations 

 2. a. a. a. 



