GROWTH OF PARASITIC FUNGI IN CONCENTRATED 
SOLUTIONS 
By Lon A. Hawkins, 
Plant Physiologist , Drug-Plant f Poisonous-Plant , Physiological , and Fermentation 
Investigations , Bureau of Plant Industry 
The mycelium of a fungus growing parasitically is frequently in con¬ 
tact with the cell sap of its host plant. This cell sap is capable of an 
osmotic pressure which would vary, of course, with the amount and nature 
of the compounds in solution. The hyphae of the invading parasite, then, 
may grow in a medium which has more or less high osmotic pressure. In 
order to grow in this medium, they must, of course, be able to withdraw 
water from it. It is apparent, then, that plant parasites must quite 
commonly possess the ability to withdraw water from more or less highly 
concentrated solutions and to grow in them. 
The relative concentration of the cell sap of parasite and host has 
received some attention in the case of phanerogamic parasites. 
MacDougal (9, io) 1 and MacDougal and Cannon (11) reached the con¬ 
clusion that for their “Xeno parasites'’ the osmotic pressure of the 
parasite must be greater than the plant into which it is transplanted. 
Senn (14), in a recent investigation, has shown for certain phanerogamic 
parasites that the osmotic pressure of the parasite, as measured by the 
plasmolytic method, is invariably higher than that of its host. This 
writer seems not to have seen the work of MacDougal. Not so much 
attention has been paid to fungus parasites, though some work has been 
done in growing fungi in concentrated solutions. Eschenhagen (4) 
grew Aspergillus niger, Penicillium glaucum , and Botrytis cinerea on 
rather highly concentrated solutions of various substances. He found 
that these fungi grew in a saturated solution of potassium nitrate at 
ordinary temperatures and that the concentration of glucose which lim¬ 
ited growth was above 50 per cent. He came to the conclusion that the 
ability of the fungi to live and grow when transferred to a higher con¬ 
centration was due to a heightened osmotic pressure within the cell 
produced by an actual increase in the osmotically active substance 
therein. 
Raciborski (13) also has shown that some fungi can live in exceedingly 
concentrated solutions. He grew Torula sp. in a saturated solution of 
lithium chlorid and Aspergillus glaucus in a similar solution of sodium 
chlorid. He considered the osmotic pressure in the cell to be greater 
than that of the outer medium and attempted to calculate the molecular 
1 Reference is made by number to “ literature cited,” pp. 259-260. 
Journal of Agricultural Research, 
Dept, of Agriculture, Washington, D. C. 
fw 
(255) 
Vol. VII, No. 5 
Oct. 30, 1916 
G— 97 
