3 8 ELEMENTARY BIOLOGY. [CHAP. 



give off very short aerial hyphae, which terminate in minute 

 sporangia. In these a very small number of ordinary 

 mucor spores is developed, but, in essential structure, both 

 the sporangia and the spores resemble those of normal 

 Mucor. 



LABORATORY WORK. 

 A. 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 will overrun with 

 Bacteria, to the exclusion of everything else. And very 

 frequently other moulds, such as Aspergillus, 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. HlSTOLOGICAL 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. Hyphcz. Note their diameter (measure) 



form subdivisions (cells] dichotomous mode 



of branching and structure: the external 



