May 2i, 1917 
Xylaria Rootrot of Apple 
275 
like masses, occurs most profusely on the incrustation on com meal. 
Bean pods or com meal in flasks appear to be most favorable for the 
formation of stromatic arms. These stromatic arms vary in size from 
very small to those having a length of 10 to 12 cm. and a diameter of 1 
cm. They are either entire or branched in a coralloid manner. The 
stromata are flesh-colored within and are generally covered, except at 
the tip, which is also flesh-colored, with a dense hirsute coating. These 
hairs are 3 to 5 mm. long and impart to the stromata a beautiful variety 
of colors, among which are gray and shades of brown, violet, and green. 
Small stromata may not possess this coating of hairs. 
A study has been made of the influence of temperature, light and 
darkness, and moisture upon the growth of this organism. For this 
purpose, several sets of cultures were prepared, one of which was main¬ 
tained in an incubator at 3 7 0 C. Scarcely any growth takes place at 
this temperature. A moderate growth of mycelium, conidia, and stro¬ 
matic arms 4 to 6 cm. long were produced in another set kept at 28°. 
Room temperatures of 21 0 to 25 0 were found to be more favorable for 
growth than this last temperature, but the most luxuriant growth 
occurred in cultures kept in an ice box at temperatures of n° to 13 0 . 
The largest stromatic arms obtained were formed at this temperature. 
Light appears to exert no morphogenic stimulus in the formation of 
stromatic arms, since these structures, both simple and branched, ap¬ 
peared in sets of cultures kept in a photographic dark room. The 
vegetative growth, too, appears to be as luxuriant in darkness as in 
the light. 
In the tests upon the influence of moisture, flask cultures containing 
12 gm. each of com meal were employed. This com meal was moistened 
by the addition of quantities of water varying from 20 to 65 c. c. After 
inoculation the cultures were incubated for six weeks at room tempera¬ 
ture. As judged by the luxuriance of growth, 40 to 50 c. c. of water 
appear to be the optimum quantity. No conidia formed in the cultures 
containing less than 40 c. c. of water. 
PATHOGENICITY 
Four apple trees only were used in making tests to determine the 
parasitism of this organism. On one tree three inoculations were made; 
on each of two others, six; and on the other, fen. These inoculations 
were made at West Raleigh, N. C., during the months of May, June, and 
September. The soil was first removed so as to expose the roots, after 
which the inoculations were effected. The inoculum, which consisted 
of mycelia from steamed-rice cultures, was either inserted into wounds 
made by scraping off the cortex, or by making incisions into it, or was 
applied to uninjured roots. The places of inoculation were then covered 
with a layer of soft paraffin. The roots inoculated varied in diameter 
from to 3 inches. Infections were uniformly successful, irrespective 
