INVESTIGATIONS OF POTATO WART. 
13 
seem to be an unfavorable tissue for the entry of zoospores or to show 
a marked growth response resulting from infection. In the tomato 
and eggplant, adventitious shoots arise from the underground portion 
of the stem, usually late in the season. Infection of these buds or of 
the shoots occurs in the tomato, but fails through the operation of an 
unknown factor in the eggplant. 
Table 3. — Solanaceous species of plants tested for susceptibility to potato wart in gardens 
at Freeland and Upper Lehigh, Pa., in 1920 and 1921. 
[Infection of all these species and varieties failed.] 
Species. 
Number of 
plants. 
Species. 
Number of 
plants. 
1920 
1921 
1920 
1921 
Solanum melonsena L. var. esculen- 
tum Ness, (eggplant): 
Chinese White 
7 
30 
13 
"""is 
""26 
14 
12 
Datura stramonium L. (stramonium). 
20 
20 
Solanum integrifolium Poir. (=S. 
9 
Nicotiana rustica L. (wild tobacco) 1 ... 
Nicotiana tabacum L.: 
12 
6 
9 
10 
5 
3 
( l ) 
IS 
6 
4 
Capsicum anninun L. (peppers): 
G 
23 
6 
G 
G 
White Burley 
Pennsylvania Broadleaf 
World Beater 
Pirn ento 
Nicandra physalodes (L.) Pers. 
(apple of Peru) 1 
Physalis pubescens L. (Burpee husk 
tomato) 
( 2 ) 
Petunia violacea Lindl. (petunia) 
12 
Solanum dulcamara L. (bittersweet).. 
8 
1 These species occur as weeds in one of the gardens most heavily infested with wart. 
* Numerous. 
While the testing of potential hosts will be continued, particularly 
with the aim of including all temperate-climate species of Solanum, it 
is believed that the failure to find new hosts among the several cul- 
tivated and most common indigenous solanaceous plants of this 
region (with the exceptions mentioned) makes it improbable that the 
Eathogen is able to maintain itself in this region on unsuspected 
osts, which therefore require particular quarantine action. 
VARIETAL TESTS WITH TOMATOES. 
The susceptibility of the tomato to infection by Synchytrium en- 
dobioticum (Schilb.) Perc. was shown by Kunkel and Orton in 1919. 15 
Tests with tomatoes have been carried on each year since then, but 
not all factors entering into the tests have been amenable to satisfac- 
tory control so it is not yet considered that complete and entirely 
reliable data as to the susceptibility of tomato varieties are at hand. 
The present state of information in this respect is shown in Table 4, 
in which are listed only the varieties that have been proved to be 
susceptible. 
The tomato is much less readily susceptible to wart infection than 
the potato, and the development of the overgrowths is always less 
marked. Infection usually occurs in buds or adventitious shoots 
on the main stalk below the soil surface. It therefore appears 
u Lyman, G. R., and others. Op. cit. 
