152 PRACTICAL BOTANY. 



yeast has decomposed the Pasteur's solution is called an 

 organized ferment. 



References for Reading. Bidgood's " Elementary Biology," pp. 

 27-44; Parker's "Elementary Biology," pp. 71-81; Huxley and 

 Martin's "Practical Biology," pp. 377-388; Dodge's "Practical 

 Biology," pp. 28-39; Carpenter's "The Microscope," pp. 574, 575. 



PENICILLIUM. PRACTICAL STUDIES. 



Penicillium glaucum is one of the most common molds. 

 It is found on a large variety of substances that are 

 exposed to the air as a blue or green mold. It may be 

 raised for study by sowing its spores on Pasteur's solution 

 or on a decoction of vegetable matter, such as was used in 

 studying Bacteria. In fact, either of these solutions, left 

 exposed to the air, will generally bear the mold after a 

 few days. It first appears as minute tufts of cottonlike 

 filaments. These tufts enlarge in diameter and grow 

 thicker in the center. The inner portions gradually 

 change to blue, and finally to sage green, so that a well- 

 developed spot has a green center, surrounded by a ring 

 of blue and a second peripheral ring of white. 



Penicillium glaucum resembles Eurotium somewhat in 

 its structure, but is readily distinguished from it by its 

 smaller size, by the color, and by the fanlike arrangement 

 of the spores in the heads. The formation of spore fruits 

 is known to occur, but their study is difficult for be- 

 ginners. 



1. Cultivate some Penicillium on Pasteur's solution or 

 hay decoction. Carefully transfer one of the smallest 

 spots to a glass slip, keeping it right side up. Do not use 

 a cover glass. Examine with the lowest power. Notice 

 the mycelium, composed of interlacing filaments ; the 

 aerial hyphse rising erect into the air ; and the submerged 

 hyphse descending into the nutrient solution. 



