Nov. i, 1915 
Potato Tuber-Rots Caused by Fusarium Spp. 
205 
Table VII .—Percentages of variously septate normal conidia , average sizes , and limits 
of size as found in a io-day-old pionnotes on Melilotus alba and in a 15-day-old 
cotton pionnotes of Fusarium eumartii. 
IO-DAY-OLD PIONNOTES ON MELILOTUS ALBA 
Septation. 
Percentage 
of conidia. 
Average size 
of conidia. 
Limits. 
5. 
7 
M 
A* 
4. 
20 
54.4 by 5.6- 
62.7 bv K .&.... 
51 to 54.4 by 5.1 to 6.1. 
59.5 to 69.7 by 5.4 to 6.1. 
66.3 to 71.4 by 6.1 to 6.8. 
68 to 76.5 by 5.9 to 6.8. 
r. 
5° 
8 
6. 
69.7 by 6.3- 
71.6 by 6.5. . . . 
7 . 
15 
15-DAY-OLD PIONNOTES ON COTTON 
3 
4 
5 
6 
7 ' 
8 , 
5 
*7 
58 
62.9 by 6.1... . 
18 
73.2 by 6.6. . . . 
2 
79.9 by 6.6. . . . 
Rare. 
85 by 6.8. 
56 to 76.5 by 5 to 6.8. 
51 to 81.6 by 5.9 to 7.2. 
74.8 to 85 by 6.3 to 6.8. 
The formation of pigment in F. eumartii (PI. A, fig. 6-8) and F. radicicola is much 
the same as that in F. solani , only more gorgeous. The conidial color fluctuates 
between brownish white and bright brown; by infiltration of the greenish blue 
plectenchymatic pigment the conidial mass becomes gray, blue-green, to brown and 
a dark mixed color. The plectenchymatic stroma is weakly developed or lacking, 
and therefore the pionnotes lies naked on the substratum. The chlamydospores, 7 to 
iOjU in diameter, agree with those in other species of this section. 
F. eumartii causes a rot of potatoes in experiments, while F. martii is said to be a 
saprophyte (20, p. 30). This statement was confirmed with F. martii 186 collected 
in Germany. The new species agrees more closely with Fusisporium solani Martius 
(8) in the size of conidia than does F. martii. 
F. radicicola and F. eumartii are very closely related to F. martii with respect to 
average size and septation of normal conidia and occupy the same relative positions 
on either side of the last-mentioned species as a type. In average measurements 
the conidia of F. radicicola are approximately 30 per cent shorter and 20 per cent 
narrower than those of F. martii (sensu strict .), while F. eumartii is larger in about the 
same proportion. F. radicicola is typically triseptate, F. martii 3- to 4-septate, and 
the new species 5- to 6-septate. Similar constant varieties of certain other species 
are known—e. g., of Fusarium solani . 
Habitat.—On decaying tubers of Solanum tuberosum from Pennsylvania and New 
York. Cause of potato dry-rot and wet-rot. 
4. Fusarium radicicola Wollenw. (21, p. 257-258). 
The conidia of this species are normally triseptate, averaging 30 to 45 by 3.75 to 5/x; 
narrower than in F. solani , sensu strict . (PI. XIV, fig. 3), and shorter and fewer 
septate than in F. martii and F. eumartii (PI. XIV, fig. 4). The plectenchymatic 
mycelium, as in the two latter species, is olive colored on potato cylinders, shading to 
green and brown. Pionnotes on potato cylinders, cotton, and stems of Melilotus alba 
brownish white to blue and verdigris (PI. A, fig. 6-8). Pigment formation the same 
as in F. martii and F. eumartii. Chlamydospores as in other species of the section. 
