Colloidal Solutions by Fungi. 533 
were of extremely small diameter, the Oidium hyphae being the easier to 
examine. 
The results were as follows: 
1. Absorption by Living Material. 
Oidium lactis. 
(a) Gold present throughout the wall, as seen in 
cross-section. 
(3) No gold retained in the protoplasm. 
(*:) Wall of spore coloured in same manner as 
wall of hyphae. 
2. Absorption 
Some coloration seen in wall of hypha. 
Distribution less uniform than in case of living 
material. 
Slight precipitation of gold on limited areas of 
surface of protoplasm. 
Penicillium glaucum. 
Wall of hyphae stained throughout its thickness. 
Protoplasm free from gold. 
Wall of spore (which is cuticularized) without 
stain or surface deposit. 
by Dead Fungus. 
Same result as 0. lactis. 
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In all the specimens examined the gold was firmly retained and could 
not be removed during the embedding, or by long washing in such liquids 
as ether, acetone, and alcohol, of very varied surface tensions. 
Method of Removal and Retention of the Gold. 
Since the colloidal gold carries a negative charge and can be precipi¬ 
tated by the addition of electrolytes, two means by which the fungus acts 
suggest themselves: 
(a) The fungus wall may possess a positive charge when in contact 
with the colloidal solution. 
( b ) Electrolytes may diffuse out of the cell at such a rate that they 
only suffice to coagulate the gold which has diffused into the wall and not 
so as to affect the liquid outside. Experiments were accordingly made to 
endeavour to find the nature of the charges upon the fungus cellulose in 
contact with water and with gold solutions. 
A microscopic cover-slip was provided with electrodes of silver foil 
fixed in position with shellac and carrying fine wires. The material to be 
examined was placed on the slide and the whole connected with a reversing 
key and battery. 
In some cases, when the current from four Leclanche cells was used, 
a well-marked migration of tiny pieces of hyphae and of spores took place, 
this movement being immediately reversed upon reversing the current. 
The direction of migration, and consequently the charges, were varied; 
thus of twelve cultures examined, six showed a negative charge, three no 
charge, while three showed a slight positive charge. 
The first suggestion of an electrical explanation was therefore not 
supported. 
