5« 
Journal of Agricultural Research 
Vol. II, No. i 
pirinum , Coryneum foliicolum y Phyllosticta limitata , Monochaetia mali , 
Phomopsis mali , and a species of Pestalozzia. Later, a species of Alter- 
naria was also employed, to which the name Alternaria mali will be given, 
though, owing to the confused state of names and descriptions in this 
genus, the identification of this species with any degree of certainty is im¬ 
possible. The description of the fungus and of its appearance when grow¬ 
ing on various artificial media serves to separate it from the two or three 
other species which occur on the apple. Its cultural characters alone serve 
to separate it from one of these species, and it differsfrom all of them in the 
possession of a minutely spiny or nearly verrucose exosporium. The 
mycelium, as is common in the genus Alternaria, is composed of olive- 
tinged hyphae rather sparingly branched. The club-shaped spores (Pi. 
VII, fig. 2) are for the most part muriform-septate, the transverse septa 
numbering usually from three to five in mature spores. The spores are 
30 to 35 by 12 to 13 fi in size, with isthmi measuring 4.5 to 7 by 3 to 4 /i. 
Its technical description is as follows: 
Alternaria mali, sp. nov.—Hyphis fasciculatis septatis subsimplicibus vei ramu- 
losis, griseo-olivaceis; conidiis clavatis, olivaceo-brunneis, 3-5 septato-muriformibus, 
ad septa constrictis, breve hispidis, 30-35X12-13 pL, isthmis 4.5--7X3-4 /*■ 
Hab. In foliis Pyri mali , Arlington, Virginia. 
The growth of Alternaria mali on culture media was as follows : 
BEEF Agar +10.—Growth diffuse, grayish to nearly black at surface; aerial 
hyphae nearly white and rather short. 
BEEF Bouillon. —Growth much as on beef agar, forming compact disk over surface 
of liquid; brownish where in contact with liquid and nearly white above. 
Prune Juice. —Growth forming disk over surface of medium, greenish black below; 
abundant flocculi of rather long aerial hyphae, which are gray, slightly tinged with 
green. 
Prune Agar. —Growth very abundant, forming dark, nearly black crust over sur¬ 
face of slant, with abundance of rather long, greenish gray, flocculent aerial hyphae, 
becoming darker green near the surface. 
Corn-Meal Agar. —Growth the same as on prune agar. 
Bean Pods. —Growth black where in contact with tube and dark gray where in con¬ 
tact with liquid. Aerial hyphae fairly long over pod and from light gray to nearly 
white. 
Potato Agar. —Growth nearly black at surface of media, with very short, scant, 
gray aerial hyphae. Greatly resembles growth on beef agar. 
Alternaria mali has several times during the last year been isolated 
from fruit of the apple by Mr. D. F. Fisher, of the Office of Fruit-Disease 
Investigations, and has been found by inoculation to cause a rapid rotting 
of ripe apples. 
Sphaeropsis malorum was also used in some of the later experiments. 
Lewis (1909, 1912) has shown that at least in Maine the first three of 
these fungi are saprophytes capable of growing and fruiting only on spots 
previously killed. 
EXPERIMENTS AND OBSERVATIONS ON THE FUNGUS 
Inoculations were made both in greenhouse and in orchard on unster¬ 
ilized leaves of susceptible varieties of apples, chiefly the Ben Davis and 
the York Imperial. Circular dead spots were made by touching the 
leaves with the heated end of a cylindrical steel rod 2 mm. in diameter. 
About 2,000 inoculations were made by spraying each spot with distilled 
water containing spores. Spots sprayed with distilled water only were 
considered as checks. The leaves were kept moist for periods of from one 
