6 
Journal of Agricultural Research 
Vol. VII, No. i 
GROUP CHARACTERIZATION 
COLONY CHARACTERS 
Colonies spread rapidly upon Czapek’s solution agar. They are at 
first white with abundant submerged mycelium and with more or less 
prostrate or trailing hyphse radiating toward the periphery. Floccose 
aerial mycelium is occasionally developed later. Conidiophores arise as 
colorless branches from submerged or, more rarely, from aerial hyphse 
and constitute the whole surface growth in most strains. With conidial 
production the colony color changes from white to fuscous black, but 
never shows any shade of green. 1 In certain forms Saito 2 records the 
color as passing through yellow to brownish black. The color found is 
rarely evenly distributed in the fruiting parts. Yellow or yellow-brown 
color may be present or absent in the upper ioo fx of the stalk; in old 
cultures it is usually found in the vesicle and sterigmata, which frequently 
are deeply colored, even becoming brownish black or carbonaceous in 
certain races. Most of the color, as indicated by the researches of 
Linossier, 3 is deposited in the ridges or warts of the conidial wall. The 
submerged mycelium is uncolored in some forms, more or less deeply 
yellowed in others. The agar remains uncolored. All forms grow at 
37 0 C. and, with the exception of A. carbonarius , are favored by that 
temperature. 
MORPHOLOGY 
Stalk. —The stalks or conidiophores vary in thickness from 6 to 25^, 
and in lengths from 0.5 to 10 mm. They are unseptate or indistinctly 
septate and have thick walls, smooth on the outside, and on the inside 
either smooth or, in some cases, with irregular thickenings. When 
broken these walls split lengthwise into strips. There is a great differ¬ 
ence in the length of stalks in the same colony. In the denser center of 
the colony, developed upon fresh media with abundant food, the stalks 
are crowded together and shortest. At the margin the scattered fruiting 
heads are borne upon stalks which may be twice to several times the 
length of those in the center. If the center of the young colony be taken 
as typical of the race, the strains in culture fall roughly into three groups: 
(1) Short-stalked, with stalks 500 to i,oooju; (2) intermediate, with 
stalks 1,000 to 3,ooom; (3) long-stalked, with stalks 3 to several milli¬ 
meters in length. The first two groups, however, certainly shade into 
each other. 
1 Ridgway, Robert. Color Standards and Color Nomenclature. PI. 46, 13"". Washington, D. C., 1912. 
2 Saito, Kendo. Mikrobiologtsche Studien iiber die Zubereitung des Batatenbranntweines auf der Insel 
Hachijo (Japan). In Centbl. Bakt. [etc.], Abt. 2, Bd. 18, No. 1-3, p. 31. 1907. 
* Linossier, Georges. Sur une h&natine veg^tale, l'aspergilline. In Compt. Rend. Acad. Sci. [Paris], 
t. 112, no. 15, p. 807-808. 1891. 
-Sur une h&natine vegetale: l’aspergilline, pigment des spores de l’Aspergillus niger. In Compt. 
Rend. Acad. Sci. [Paris], t. 112, no. 9, p. 489-492. 1891. 
