Jan. 17,1916 
Plenodomus fuscomaculans 
759 
increase of food supply we must now consider, besides the mere chemical 
parts, the ratio of these parts to each other, both at the outset of growth 
and throughout the growing period. We analyze such relations and 
classify them as reaction, etc. 
For pycnidium production the limits are found to be much narrower 
than those suitable for growth. No reproduction takes place at the 
base level of existence. Food supply must be increased, not greatly, 
but in measurable amount. From the scanty supply in conductivity 
water it must increase to the quantity found in distilled water—a two¬ 
fold to tenfold increase. Or it must be present in at least one thousandth 
of the quantity cooked from a few sheets of finest filter paper by conduc¬ 
tivity water, but one-tenth of this amount is not sufficient. Oxygen 
must be present in abundance; stagnant air prevents reproduction. The 
temperature may be as low as io° C., but must not be as low as 6K° C. 
Up to a certain limit (perhaps up to M/50), increase in concentration 
of the food supply augments reproduction. After that point the excess 
food supply retards and eventually inhibits reproduction. Fructifica¬ 
tion, when it does take place with media of higher concentration, takes 
place in the aerial mycelium, and doubtless here the conditions are com- 
* parable to those in which the fructification is produced within or upon 
the medium. 
The kind of food may vary almost without limit. An organism which 
can grow and reproduce in distilled water or a grain of com can find 
requisite food materials in almost any biological product. But the 
more complex substances bring new relations, which, while of some 
importance to growth, are of decisive importance for reproduction. 
Growth can take place between the acid and alkali limits of + 30 and —10 
to phenolphthalein, but reproduction is limited to the conditions but 
slightly more acid than the neutral point of this indicator. 
Corn broth seems at first glance a better foodstuff for this organism 
than oat broth, and in two parallel cultures the first will produce 50 
pycnidia while the other is producing one. Yet if the oat culture be 
acidified with an acid phosphate, or even with hydrochloric acid, it 
becomes nearly as good a culture medium as the corn. Glucose agar made 
after the ordinary formula gives a strong growth with this organism, but 
no pycnidia. If the chemicals of this formula be diluted 50 times, the 
organism will fruit abundantly upon it. This organism was found to be 
greatly overfed by the ordinary laboratory media, and under the influence 
of the great excess of food grew and grew until the by-products of 
metabolism checked growth or destroyed the organism. 
The differences in media were not so much in the food which they con¬ 
tained—for an examination of published analyses will show all necessary 
elements for growth and reproduction in almost any plant—as in the acid 
or alkaline reaction which the medium gave when prepared, the reaction 
maintained, and the concentration or relative scantiness of carbohydrate 
