274 
Journal of Agricultural Research 
Vol. IX, No. 8 
whether this perithecial form is genetically connected with the conidial 
stage which appeared in culture. The perithecial material is morpho¬ 
logically quite like Xylaria hypoxylon , a species in which is included a 
wide variety of forms. It is quite probable that several species of Xylaria 
are involved in this diseasef^s has been suggested by Fromme and 
Thomas, 1 who found Xylaria polymorpha associated with apple rootrot 
in Virginia. 
cultural characters 
Various kinds of nutrient agar were found to be unfavorable sub¬ 
strata, since on them growth proceeded slowly and there was only a 
slight tendency toward the formation of a black incrustation and rhizo- 
morphs. When agar added to decoc¬ 
tions of apple fruits or roots was 
employed, and also when sterilized, 
well-moistened apple roots were used 
as a culture medium, an abundant 
mycelium and a well-developed in¬ 
crustation were produced. No fruc¬ 
tifications have been noted on these 
media, however, even in cultures 
which have been kept growing for 
three years. 
The general appearance of the 
mycelium on various culture media 
is quite like that on decaying apple 
roots. The young filaments (fig. 3, 
b y d ) are hyalin, branched, granular, 
and highly refractive, with an aver¬ 
age diameter of only 2 to 3 /*. Con¬ 
siderable variation in the diameter 
of the filaments occurs, as indicated 
in figures 2, b t and 3, a. Later, the 
hyphse lose their granular contents, become brown to olivaceous in color, 
and numerous blunt, spinulose terminals are developed (fig. 3, c, /). 
Filaments in old cultures become more closely septate, the cells may 
attain a diameter of 4 to 8 jit (fig. 2, b) and are chlamydospore-like, in 
that they retain their vitality even after desiccation for several months. 
Fusion of hyphse, as shown in figures 2, a, and 3, e> has occasionally been 
noted. 
On potato plugs, steamed com meal in flasks, bean pods, and other 
sterilized plant parts, a copious mycelial growth is produced, which may 
become crustlike; and, in addition, stromatic arms and conidia are 
formed. Conidial formation, in reddish brown or grayish sporodochia- 
Fig. 3.— Xylaria sp.: Mycelium, showing (a) con¬ 
siderable variation in the filaments; b, d t the young 
filamentsare hyalin, branched, granular, and highly 
refractive, with an average diameter of 2 to 3 /*; 
c, /, the hyphse later lose their granular contents, 
become brown to olivaceous in color, and numer¬ 
ous blunt spinulose terminals are developed; e, 
fusion of hyphse. 
1 Fromme, F. D., and Thomas, H. E. Toe. cit. 
