APPENDIX. 23 I 



shallow dish, and a temperature of 35 C. proved to be 

 the most favourable. The abstraction of zinc from the 

 nutritive liquid reduced the weight of a crop from 25 (the 

 average) to 2 grammes, and the presence of T^woire 

 part of nitrate of silver, or MFOITO part of corrosive 

 sublimate, stopped the growth altogether. It is sapro- 

 phytic in the living body. 



METHOD OF EXAMINING ASPERGILLUS NIGER. 



Species of aspergillus stain intensely with carmine, 

 fuchsine, or methyl-violet, but to examine Aspergillus niger 

 with a high-power, a little special technique is employed, 

 as follows : A drop of glycerine is placed on a clean 

 slide, and a drop of alcohol on a cover-glass. With a 

 fine pair of forceps a few of the fruit hyphae with their 

 black heads are immersed in the alcohol. The cover- 

 glass is then turned over on to the drop of glycerine, and 

 the slide held in the flame of a Bunsen burner till the 

 spores or conidia are dispersed. To make a permanent 

 preparation, remove the cover-glass, and transfer the fruit 

 hyphse so treated to a mixture of glycerine and water 

 (i to 5) ; a drop may be conveniently placed ready on a 

 slide provided with a ring of Canada balsam. The speci- 

 men is then permanently mounted by employing a circular 

 cover-glass, and surrounding it with a ring of cement in 

 the usual way (Plate XXIX., Figs. 8 and 9). 



Aspergillus ochraceus. At first flesh-coloured, 

 and then ochre-yellow heads. 



Aspergillus albus. Pure white fruit heads. 



Aspergillus clavatus. Club-shaped fruit head* 

 on long stems. 



Penicillium glaucum. Occurs as a white, and 

 later a blue-green mould, on which dewlike drops of 

 liquid may appear (Plate IX., Fig. 2). Its spores are 

 present in large numbers in the air, and are liable to 

 contaminate cultivations. Diam. of the spores '0035 mm. ; 

 threads vary in diameter between '004 and "0007 1 mm., 



