Aug. u, 1923 
Irish Potato Foliage Degeneration Diseases 
263 
lieved to be incidental so far as its connection with net-necrosis is con¬ 
cerned. A study of Table I will reveal the fact that leafroll resulted 
in every case of spindling-sprout, either alone or associated with mosaic, 
while there was no case of spindling-sprout observed when mosaic 
alone appeared in the resulting plants. On the other hand, numerous 
cases of mosaic of both the mild and extreme types were recorded in 
plants from tubers with normal sprouts. Similar conclusions are 
reached with reference to net-necrosis—that is, that while both mosaic 
and leafroll symptoms have been noted in plants from net-necrosis 
tubers, in no cases have such tubers resulted in plants exhibiting mosaic 
symptoms only. Net-necrosis, therefore, of the type discussed and 
illustrated in the present paper, is definitely and closely correlated 
with spindling-sprout of the tuber and with leafroll of the plant. 
Table III .—Showing correlation of spindling-sprout and net-necrosis of the tuber with 
leafroll of the foliage 
Lot No. 
Number 
of tubers. 
Condition of 
sprouts. 
Net-necrosis. 
1 
Number 
of hills. 
Condition of foliage. 
87. 
1 
Spindling.... 
Present.... 
4 
Leafroll and mosaic. 
80. 
I 
.do. 
.do. 
2 
Do. 
01. 
8 
.do. 
.do. 
O 
20 
Leafroll. 
06........ . 
1 
.do. 
.do. 
A 
Do. 
108. 
■2 
.do. 
.do. 
1 
1 2 
Do. 
Ill. 
O 
2 
.do. 
.do .... 
O 
4 
Do. 
APICAL DOMINANCE 
Appleman in an article entitled “Some Factors Influencing the 
Vitality of Seed Potatoes" (4) in Maryland Farmer, volume 5, No. 16, 
1921, states that “good normal tubers will as a rule sprout first from 
the seed or apical end," and also that “lack of apical dominance is a 
sign of low vitality in the tuber or in other words of its inability to pro¬ 
duce vigorous plants." In another publication (3, p. 80) this author 
says: “The greater vigor of the terminal shoot may be due to greater 
inherent strength of the terminal bud or it may be merely apparent 
because the temimal shoot inhibits the growth of the lateral ones. The 
latter view suits best the requirements regarding the growth of buds on 
the potato tuber." He further states that while, under uniform con¬ 
ditions, terminal buds ordinarily grow out first, still if the basal eyes 
are more favorably situated with respect to the action of external agents 
the suppression of their growth by terminal buds may be entirely over¬ 
come. These facts are understood to be true only of the first crop of 
sprouts from a tuber. 
In connection with the studies reported in the present paper many 
observations have been made as to the manner of sprouting of diseased 
and healthy tubers ,some of which have a bearing upon the matter of 
apical dominance. Tubers with normal sprouts from the apex and with 
the other eyes dormant were selected for planting and also those with 
normal sprouts from various eyes scattered over the tubers. Table IV 
gives the results of the observations upon the plants grown from these 
tubers. 
