1055 
June 1,1925 Comparative Studies of Pythium debaryanum 
6, A, h). The endospore wall is dis¬ 
solved, and a single thick tube breaks 
the exospore and oogonial walls. The 
contents of the oospore gradually pass 
into the tube, which continues to grow 
and form a mycelium. Zoospore for¬ 
mation has not been observed. • 
CULTURAL STUDIES 
The cultural characters of these 
fungi were studied along with those 
of Pythium complectens, on 16 media 
in 4 culture series. The terminology 
suggested by Harsch and Long (IS) 
and also followed recently by Fritz 
(11) has been followed in describing 
the character of growth. These stud¬ 
ies have shown specific differences 
which have remained constant since 
original isolation. Except on four 
media, the four fungi were readily 
distinguishable from each other ma- 
croscopically. Cultures of each or¬ 
ganism were always made in triplicate 
tubes on each medium. Some of the 
more prominent diagnostic characters 
are as follows: 
On oatmeal agar and on sugar-beet 
agar the growth of A plugged the tube 
up to the top of the slant, forming a 
narrow, compact web across the bore. 
This persisted when the rest of the 
mycelium below it had matted down. 
No such web was formed by the other 
fungi (pi. 7, A and E.) 
The growth of D on most media was 
sharply characterized by being much 
more compact and appressed to the 
slant than that of A or B, This may 
be seen in the side views of the tubes 
in plates. 
Np aerial growth was produced by 
A on cornmeal agar, carrot agar, 
potato agar, potato dextrose agar, and 
potato cylinders (slight aerial on the 
last after four weeks), contrasting 
sharply with the, abundant aerial 
growth of the other two fungi (pi. 8.) 
A characteristic feature of A was 
the granular appearance of all cultures 
due to the abundant production of 
large conidia. 
Growth of B on potato cylinders 
was distinctive, due to the abundance 
of loose, fluffy aerial mycelium. That 
of A was entirely prostrate, that of D 
was feltv, compact and closely ap¬ 
pressed to the cylinder. 
The media used throughout was 
prepared uniformly in accordance with 
the formulas of the Laboratory of 
Plant Pathology. Directions as given 
by Smith (19) were followed in the 
case of nutrient beef-broth agar, 
potato cylinders, sugar-beet cylinders, 
and bean pods. The formulas for the 
remainder were taken from the files 
of the laboratory and are appended. 
CORNMEAL AGAR 
To 4 teaspoonfuls of com meal add 1 liter of dis¬ 
tilled water. Keep in water bath for 1 hour, tem¬ 
perature about 50° C. Filter through cotton. 
Add li4 per cent agar flour to the filtrate. Steam 1 
hour, filter through cotton, tube, and sterilize in 
the autoclave for 15 minutes at 115° C. 
OATMEAL AGAR 
50 gm. oatmeal in 500 c. c. H 2 O. Steam in bath; 
strain through gauze; add 2 per cent agar flour 
(mixed in cold water); make up to 500 c. c.; steam, 
tube, and autoclave 15 minutes at 115° C. 
CARROT. SUGAR-BEET, STRING-BEAN AGARS 
Wash thoroughly, weigh and add water to double 
the weight of solid material. Let simmer. Strain 
and add \\i per cent agar flour; steam three-quarters 
of an hour, filter, tube, autoclave or steam. For 
geranium agar, use twenty times as much water, 
3 per cent agar, and steam. 
POTATO AGAR (STRONG INFUSION, OXIDIZED) 
500 gm. potato, 1,000 c. c. distilled HiO, O/i per 
cent agar flour; weigh potatoes, put through meat 
grinder, add water, and let stand 1 hour. Strain 
through gauze to remove cellulose. Make up to 
volume. Steam juice to clarify, and filter through 
cotton. Add agar, steam three-quarters of an hour. 
Filter through cotton, tube, and autoclave for 15 
minutes at 115° O. 
Potato dextrose agar: Add 10 per cent dextrose. 
CONGO-RED AGAR 
To 1,000 c. c. distilled HiO add 10 gm. saccharose 
(Mercks); lgm. K 2 HPO 4 (dipotassium phosphate); 
0.20 gm. MgSOi (magnesium sulphate); 15 gm. agar 
flour (powdered); 0.10 gm. congo-red (powdered 
Gruhler’s). Steam water and all salts for one-half 
hour, then add the congo-red. Filter through cotton 
and tube. Tube, autoclave for 15 minutes at 115° 
C. 
MILK RICE (SOYKA) 
(1) Measure out 50 c. c. nutrient bouillon and 
150 c. c. milk and mix thoroughly. (2) Weigh out 
100 gm. rice powder and rub it up in a mortar with 
the milk and broth mixture. (3) Fill the paste into 
sterile tubes. (4) Sterilize in the steamer at 100° C. 
for 30 minutes on each of 3 consecutive days. (A 
pure white opaque medium is thus formed.) 
CORNMEAL FLASKS (FOR THE CULTIVATION OF FUNGI) 
Into a 100 c. c. Erlenmeyer flask put a heaping 
teaspoonful of cornmeal-. Put in enough distilled 
HaO to thoroughly wet and with a little surplus. 
Stir round to mix, plug, and autoclave foi 25 minutes 
at 120° C. 
Oatmeal agar. — A. Abundant cob¬ 
webby white mycelium plugging tube 
up to top of slant; characterized by 
the formation of a compact web across 
the bore of the tube at the top of the 
slant, persisting after the growth below 
has matted down (three weeks). Vague 
outline at base. 
B. Differs from A in the absence of 
a covering web, in the more compact 
mycelium, and in the sharp outline of 
the growth at the base of the slant 
against the glass. 
D. More compact than B, white 
growth, plugging tube only halfway up 
slant; sharp outline at base. 
