APPENDIX A. 



The following short description of several of the common species of 

 fungi and other micro-organisms met with in the course of ordinary 

 laboratory work, will, we hope, prove of value. 



No attempt is made to give a complete classification or resum'e of 

 known species, which will be discussed at length subsequently. The 

 means of their recognition here supplied will aid the investigator in 

 the detection and exclusion of possible contaminants. 



The naked eye appearances of the growths, as seen on or in various 

 nutritive media, and their microscopic characters, will be shortly de- 

 tailed in the case of each. 



PENICILLIUM GLAUCUM. 

 Naked Eve Appearances. 



This is the commonest form of cheese mould, and is recognised 

 when growing on cheese by its delicate blue colour and soft fluffy 

 appearance. Its spores are constantly present in the atmosphere in 

 such large numbers that it is one of the most frequent causes of con- 

 tamination in cultivations. It will grow on the most varied substances, 

 and the rapidity of its growth enables it to overpower and exterminate 

 other growths with which it comes in contact. It prefers free surfaces 

 for its growth. 



On Potato. — It forms a velvety blue-green covering, dotted over 

 here and there, ifthesoilbe moist, with spherical drops of clear fluid, 

 which are exhaled by the fungus. If the surface of the growth be 

 touched, a fine grey powder of spores, like the down from a butterfly's 

 wings, adheres to the surface with which it has come in contact 



On Bread Paste. — The growth is similar, but a little more luxuriant, 

 i.e., the moss-like layer of fungus is thicker than when growing on 

 potato. 



In Jelly. — On surface, as in two preceding soils (Fig. 46, p. 89). 

 It forms a blue pellicle, which floats on the layers of gelatine imme- 

 diately below it, which in the course of time has become liquid. 

 In centre, as small nodules, with fine silky rays proceeding from 

 them in all directions (Fig. 43, p. 87). 



In Liquids {Urine, Broth, &^c.). — As isolated spheres, each the pro- 

 duct of a single spore. These spheres are soft delicate globes lying in 

 the lower layers of the liquid, often of large size, and of a semi-trans- 

 parent grey tint. 



