A leaf disease of Walnuts 
69 
differences might be due only to certain differences in hosts, inoculations 
were made both with pure cultures and with conidia from the leaves of 
the English walnut upon Car y a illinoensis (Wang.) K. Koch., C. ovata 
(Mill.) K. Koch., C. cordiformis (Wang.) K. Koch, (which includes 
C. amara Nutt.), and Juglans nigra L. In all cases the leaves were 
placed in moist chambers lined with moist filter papers to render the 
atmosphere as humid as possible. The conidia from the living leaves of 
English walnut were placed in small drops of water upon both surfaces 
of the leaves. A portion of a colony together with adhering agar was 
applied in case pure cultures were employed in making inoculations. These 
inoculations were several times repeated during the summer and fall using 
leaves of different ages but in no case were infections secured. That the 
conidia used for inoculations were viable is known since some were removed 
from the drops of water on the leaves, examined microscopically, and 
observed to have germinated. It has been noted, too, that pecans and 
black walnuts growing near the diseased English walnuts, at distances of 
less than 100 feet, have never been observed to be attacked by Cylirdro- 
sporium. From this evidence it would seem that the species of Cylindro- 
sporium is distinct from C. caryogenum and probably occurs only on the 
English walnut. Smith (1. c. p. 320) reports, too, that the natural occurrence 
of bacteriosis of the walnut or walnut blight is probably confined to the 
English walnut or to its hybrids with the black walnut, which might 
be regarded as evidence of the possible restriction of the leaf spot organism 
to the same host. Even though the microscopic differences are insignificant, 
it seems advisable, to regard this only as a coincidence, in view of the 
failure to secure infections upon a closely related species, /. nigra , and 
upon a closely related genus, Carya, one species of which is the type 
host for C. caryogenum. On this account the name Cylindrosporium 
juglandis is proposed for the form causing a leaf disease of Juglans regia 
and the following Latin diagnosis is given: 
Cylindrosporium Juglandis: Maculis foliicolis amphigenis, 
numerosis, irregulariter rotundatis v. angulosis, minutis, demum 5 mm 
diam.; brunneolis, centro albicanto, quandoque confluentibus, arescendo- 
marginatis; acervulis hypohyllis, minutis, subcutaneis, erumpentibus, 
pallidis, 75—100 mm diam.; conidiis clavatis, curvulis, pluriseptatis, 
guttulatis, granulosis, hyalinis, 20—50 x 3 —3,8 ju . 
Hab. in foliis vivis Juglandis regiae, quae desidere faciunt. 
terson, of Washington, D. C. ; Prof. Atkinson reports that the two “are closely 
related, although the spots are very different. This may be due to physiological con¬ 
ditions of the host in relation to the parasite“. — Mrs. Patterson is of the same 
opinion in that she states that “according to conidial characters it does not differ 
essentially from the description of C. caryogenum E. et E. Macroscopically the diffe¬ 
rences are considerable, inoculations from your material upon Carya spp. might be 
advisable, as thereby the macroscopic effect of the parasite upon a closely related 
genus might be demonstrated”. Thanks are herewith tendered to each for this advice 
and help so kindly given. Thanks are also due Prof. Atkinson for suggestions and 
criticism in the preparation of this manuscript. 
