146 
Journal of Agricultural Research 
Vol. XXI, No. s 
The fact that the seed coat is so often carried up into the air by the 
cotyledons greatly increases the possibility of cotyledon contamination 
from the surface flora of the seed. The passage of the organism from the 
seed coat to the cotyledon should be readily facilitated by the continuous 
film of water which is often noted on the adhering seed coat. 
O11 March 9, 26 days after inoculation, some of the seeds from lots A 
and C were planted in sterile sand in glass damp chambers. Seventeen 
days later, 12 of the 115 seedlings from lot A, or about 10 per cent, showed 
primary cotyledon lesions, and none of the seedlings from the disinfected 
seed of lot C showed infection. One hypocotyl lesion was noted. 
To summarize the results of these tests, it should be noted that: (1) In¬ 
oculated seeds gave rise to diseased seedlings; (2) about 10 per cent of the 
seedlings showed primary cotyledon lesions; (3) primary lesions were 
characteristic and seemed to bear a distinct relation to the seed coat; 
(4) 26 days of drying did not reduce the incidence of primary infection; 
(5) surface disinfection of inoculated seed prevented seedling infection. 
RELATION OF PARASITE TO HOST TISSUE 
MODE OF ENTRY 
Field observation indicates that fruit infection occurs through an insect 
puncture. Inoculation tests prove that no infection of fruit occurs unless 
the epidermis of the fruit is mechanically punctured. With a bacterial 
disease this condition is to be expected, since there are no natural open¬ 
ings such as stomata in the epidermis of a tomato. The inoculum does 
not necessarily need to be inserted into the puncture, but when applied 
to the surface of the fruit the bacteria may enter fresh punctures pre¬ 
viously made. Sections through natural lesions sometimes reveal the 
presence of a puncture wound (PI. 27, A). A species of stink bug has 
been observed puncturing green tomato fruits in the field, and infection 
might readily occur through wounds caused by this insect. 
Leaf infection apparently occurs through stomata. The abundance of 
the lesions resulting from inoculation of the lower leaf surfaces as com¬ 
pared with the scarcity of lesions resulting from inoculating the upper 
surfaces has been previously noted. To illustrate this relation a further 
analysis of one of the greenhouse inoculation trials is presented in Table V. 
Each pair of plants received similar treatment in all respects except as 
noted. Atomizer inoculation was used. To facilitate inoculation of tl e 
lower epidermis of the leaves, the small potted plants were suspended 
upside down in a ring stand. 
