M. C. COOKE ON MICROSCOPIC MOULDS. 53 



sodden wash-leather, which, being placed in a saccharine solution, 

 induces acetous fermentation, and converts the solution into a sort 

 of Robinson Crusoe apology for vinegar. So long as there is 

 plenty of nourishment the mycelium, of which this production is 

 composed, continues to grow rapidly, but it does not advance 

 beyond that stage ; it vegetates, but it produces no fruit. The 

 conditions being altered, it sends up threads which bear neck- 

 laces of spores, and the "vinegar plant" proves itself no other 

 than Penicillium crustaceum. Ropey vinegar and ropey wine are to 

 be traced to the same source. For experiments in examining and 

 mounting moulds this is one of the best, since it can easily be ob- 

 tained in an almost unlimited supply at almost any season of the year. 



We pass on now to the other "blue mould," which differs 

 materially from the Penicillium in the structure of the heads. It 

 is found on all kinds of decaying vegetable and animal matter, 

 and is about the same size. To the naked eye, perhaps, very 

 similar, unless that eye is an experienced one in detecting moulds. 

 The threads are simple absolutely ; that is, they are not branched 

 at all at the top, as in Penicillium, but instead thereof the top of 

 the stem is inflated into a little globose head, and necklaces of 

 spores are seated upon, and radiate in all directions from this head. 

 This is Aspergillus glaucus. 



If a tuft of this mould be placed in a drop of water, on a glass 

 slide, and submitted to the microscope the spores will be seen ad- 

 hering more tenaciously to the apex of the thread than in Penicil- 

 lium, especially those which are seated directly upon the swollen 

 tip. The grumous gelatinous appearance of the head supplies a 

 sufficient reason for this adherence. In another species, closely 

 allied, elongated slender sporophores intervene between the head 

 and the chains of spores. 



Plates iv., v., vi., vn., vin. 



(Continued at page 61.) 



