250 
Journal of Agricultural Research 
Vol. VII, No. s 
on practically all of the common media. Since its growth does not differ 
in any essential characteristic from that of other species of Phoma, only 
the following brief cultural characters need to be mentioned: On sweet- 
clover stems the growth is fluffy, profuse, and white, turning gray with 
age; the pycnidial development is good, especially when little moisture 
is in the tube; the pycnospores often ooze to the surface. On potato 
hard agar its growth is profuse; the mycelial growth becomes evident 
within three or four days, is whitish at first, and at the end of a week 
begins to darken to the characteristic gray of Phoma spp.; the pycnidial 
development is very scarce. On potato cylinders the growth is fluffy 
and white, turning to gray within eight or nine days, the entire culture 
turning dark after the development of numerous pycnidia. On corn 
meal there is a profuse mycelial growth, at first light gray, turning 
darker with age; numerous pycnidia. On Beyerinck’s agar the mycelial 
growth is scarce and white, and this medium is especially favorable for 
the production of pycnidial bodies (Pi. 12, fig. C, D). 
By actual measurements it was found that there is no difference in 
size between the pycnospores from the host and those produced in cul¬ 
ture, those from both sources, with occasional exceptions, varying from 
3.7 to 6.0011 in length and 1.8 to 3.7// in width (Pi. 12, fig. E). 
TAXONOMY OF THE FUNGUS 
Saccardo lists four species of Phoma (14) as occurring on Solarium tu¬ 
berosum: Phoma nebulosa (Pers.) Mont., P. eupyrena , P. solani Cook and 
Harkn., and P. solanicola Prill, and Delacr. The original description 
of P. solanicola (13) states that it was found on the stems, but it was 
impossible to determine from the literature whether the three others 
were associated with the aerial part of the plant or with the tuber. The 
measurements for each of these four species and for the one under dis¬ 
cussion are given in Table XVI. 
Table XVI. —Size of different species of Phoma occurring on Solanum tuberosum 
Species. 
Size of pycnidia. 
Size of spore. 
Phoma nebulosa . 
135-145x110-115 
25 ° (f'k mm-”) 
Minute. 
7 - 5-3 
4-1/? 
Phoma eupyrena . 
Phoma solani . 
7-8 X lK-2 
6-7X4 
3. 78-6. 10 X I. 8-3.7 
Phoma so lanico la . 
Minute. 
Phoma sp. under consideration.. 
90-260 X 80-160 
Unfortunately it was impossible to obtain authentic material of the 
four species described. The original descriptions are too meager to enable 
one to identify a species with any degree of accuracy, but they show that 
in size of the spores the species differ markedly from the Phoma sp. under 
