1899] TOXIC EFFECT OF DELETERIOUS AGENTS 291 
towards the cathode when a current of electricity is passed 
through the solution, while those charged with negative elec- 
tricity migrate in the opposite direction towards the anode. As 
we have already said, a solution of HCl is about 80 per cent. 
ionized. This percentage of ionization increases with each 
; a n 
ee of dilution, becoming practically complete at eo 
‘the case of HCl. Limited space forbids further discussion of 
this interesting and important phenomenon. For further infor- 
‘mation the reader is referred to the excellent papers by Drs. 
Kahlenberg and True (’96) and Mr. F. D. Heald (’96), or to 
the more recent text-books on physical chemistry. Suffice to 
Sayin this place that the ionization of the molecule has enabled 
chemists and physiologists to determine in many cases the toxic 
, dlement or group in poisonous compounds. We shall have occa- 
og to refer frequently to this matter in discussing the experi- 
‘Mental data presented in this paper. 
_ Ithas been the writer’s aim to supplement the work of Drs. 
/Mahlenberg and True, and Heald on phanerogams, and Drs. 
Kronig and Paul (’97) on bacteria, by applying the theory of 
— of the molecule to the study of the physiology of 
cides, 
METHODS. 
Selection of forms—In the selection of forms the following 
Were given particular consideration: (@) regularity Of 
ation, (6) ability to grow normally in liquid media, (c) 
fo fruit normally in a saturated atmosphere. After 
silentation with a large number of forms the following 
chosen as being well suited for the work: Aspergillus flavus 
nk, Sterigmatocystis nigra v. Tieghem, Edocephalum albr- 
accardo, and Penicillium glaucum Link. otrytis vulgaris 
S afterwards chosen as a fifth form, it being entirely satis- 
in regard to germination and mycelial development, and 
y desirable because of its semi-parasitic habit; it, how- 
iled to fruit in cell cultures. Pure cultures of these 
