v.] ' MOULDS. 37 



LABORATOKY WORK. 



1. PENICILLIUM. 



Prepare some Pasteur's fluid, and leave it exposed to the 

 air in saucers in a warm place : if Penicillium spores are at 

 hand add a few to the fluid in each saucer : if spores cannot 

 be obtained, the fluid, if simply left to itself, will probably 

 be covered with Penicillium in ten days or a fortnight. 

 Sometimes, however, the fluid Avill overrun with Bacteria, to 

 the exclusion of everything else. And very frequently other 

 moulds, such as Aspergillus, or Mwcor, may appear instead of 

 or along with Penicillium. 



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

 upper surface, vifhite 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 



o. HyphcB. Note their diameter (measure) — form 

 — subdivisions {cells) — dichotomous mode of 

 branching — and structure : the external homo- 

 geneous sac ; the granular less transparent pro- 

 toplasm ; the small round vacuoles. Draw. 



