258 
Journal of Agricultural Research 
Vol. XXV, No. 6 
condition of the plant was very marked. There was a spindling habit, 
foliage area was reduced, and in some instances brown necrotic regions 
had developed on leaves, petioles, and stems, and premature defoliation 
had occurred. Plate i, C, shows a plant in which these symptoms were 
observed under greenhouse conditions. 
In Table I it will be noted that several samples are recorded as exhib¬ 
iting both mosaic and leafroll symptoms. In these cases the leafroll 
may perhaps be considered as the more significant since it is here asso¬ 
ciated with net-necrosis and spindling-sprout. The two infections com¬ 
bined seem to produce a condition of extreme weakness and low yield, 
more marked than would result, except occasionally, from either disease 
alone. The plants shown in Plate 6 also illustrate the double infection 
described. In these plants the symptoms of both foliage troubles were 
easily recognized. There is the mottling and wrinkling of leaflets, 
shortened petioles, and crowding of leaflets typical of mosaic, and, in 
addition, the rigid texture, the rolling of leaves, and the “staring” 
habit characteristic of leafroll. 
Table I furnishes evidence on several points as follows: (a) The data 
tend to substantiate the statement made in another portion of this 
paper that spindling-sprout is correlated with leafroll but not with 
mosaic. It will be noted in this connection that mosaic symptoms are 
recorded as associated with leafroll in some of the plants from spindling- 
sprout tubers, but that no cases of leafroll are cited as occurring in 
the plants from normal sprouts. It is not to be assumed that symptoms 
of leafroll do not occur in plants from tubers with normal-appearing 
sprouts, but it is evident that there is a correlation between spindling- 
sprout and leafroll and, further, that this is independent of the mosaic 
symptoms. ( b ) Tubers with normal sprouts produced either mosaic or 
healthy plants and in general larger yields than tubers with spindling 
sprouts. The hill yields of the tuber units show a fairly uniform decrease, 
being largest in hills from bud-end seed pieces and smallest in hills from 
stem-end pieces. This was true not only of the leafroll and mosaic but 
of healthy tuber units. 
Table; I. — Yields by tuber units from spindling-sprout and normally sprouted seed 
Record No. 
(1921). 
75 (1&-1) • • 
76 (16-2) a . 
77 (16-3)-. 
82 (18-2) .., 
85 (19-2)- 
86 (19-3).... 
87 b . 
89 * * 6 . 
7 8 (17-1)- 
79 (17-2)- 
80 (17-3)- 
81 (18-1)- 
83 (18-3) 
84 (i9-i)- 
90. 
Condition 
of sprouts. 
Spindling. 
_do_ 
-do_ 
_do_ 
.do.. 
.do.. 
.do.. 
.do., 
Normal, 
.do.. 
.do.. 
.do.. 
.do.. 
.do.. 
.do.. 
.do.. 
Yields in grams of tuber unit 
hills— 
184.1 
224 
in 
117 
60 
87 
139-9 
513 
327 
282 
304. 8 
b. 
116 
182.8 
67.3 
116 
35 
41-5 
79-4 
421 
276.5 
230 
254 
67.5 
194-5 
39 
26. 5 
31.4 
362 
263 
206 
d. 
93 - 7 
124.5 
40 . 5 
.23.5 
175 . 7 
184.5 
115 
45 
256 
Total. 
506.3 
982.4 
231. 7 
258 
233 
145 
1599 
219.3 
659 
760.8 
47 i. 7 
958 . 7 
232 
051 
833 3 
588.8 
Aver¬ 
age per 
hill. 
101. 2 
196.4 
77. 2 
64.5 
106. 5 
36. 2 
53-3 
109. 6 
164. 7 
253-6 
3679 
191. 7 
46.4 
262. 7 
208.3 
279.4 
Condition of plants 
(1921). 
Leafroll. 
Do. 
Leafroll and mosaic. 
Very weak leafroll and 
mosaic. 
Leafroll and mosaic. 
Leafroll. 
Leafroll and mosaic. 
Do. 
Mosaic (medium). 
Healthy. 
Do. 
Do. 
Mosaic. 
Do. 
Healthy. 
Mosiac. 
a It is possible that an error in placing the seed pieces is responsible for the larger yield of hill e in this sam¬ 
ple, since such a result is not in harmony with those from the other tuber units. 
6 Tubers showed net-necrosis when cut. 
