400 BOTANICAL GAZETTE [ DECEMBER 
bottom of the cell instead of a solution similar in composition 
to that forming the hanging-drop. The variation in the toxic 
value indicated from the actual value will depend on the vapor 
pressures of the solutions used. Volatile—especially highly 
volatile—and hygroscopic solutions will show the greatest error. 
10. Many deleterious agents which at certain concentrations 
retard germination and early growth, afterwards cause a great 
acceleration of mycelial development in these retarded cultures. 
This abnormal development of mycelium is usually accompanied 
by retardation of fruiting. 
11. In the conidial stage the protoplasm of molds is in gen- 
eral more sensitive to the action of deleterious agents than at 
any other stage in their life history. 
12. The effect of the different deleterious agents on the 
appearance of the mycelium is very varied and often quite 
characteristic. 
13. One is not justified in drawing any conclusions as to the 
killing powers of an agent from its effect in inhibiting the ger 
mination of the spores. 
14. The hydroxyl group OH is rather more toxic to molds 
than ionic H. 
15. The toxic value of the halogens, Cl, Br, and I, in the 
ionic state, increases somewhat in the order of increasing atomic 
weight. 
16. The cyanogen radical is a very powerful poison to fungh 
KCN having nine times the toxic value of HCl. 
17. Mercuric chlorid and silver nitrate are about equally 
toxic to molds; and are followed in toxic properties by potas- 
sium dichromate and chromate, and formaldehyde. 
18. Strychnin and hydrocyanic acid, both extremely fatal 
poisons to the higher animals, and both supposed to act 0” the 
protoplasm of the nerve cells, react very differently toward 
fungi. To the molds strychnin is practically non-toxic, whereas 
hydrocyanic acid is a very violent poison. 
19. Nickel, cobalt, iron, copper, and zinc inhibit mo 
in the order named. Zinc is much less toxic than the oth 
ld spores 
ers. 
