2o6 



Journal of Agricultural Research 



Vol. XV. No. 3 



Because of the bearing which these questions might have on distribution^ 

 overwintering, and control, 12 horticultural varieties of cucumbers and a 

 large number of other cucurbits were tested as to susceptibility to angular- 

 leafspot. The varieties of field cucumbers and the other species and 

 varieties of cucurbits which are listed in the following table were grown 

 in a cucumber field thoroughly infested with angular-leaf spot, where they 

 were under the most favorable conditions for infection. The varieties of 

 forcing cucumbers were tested by inoculation in the greenhouse. 



Plants exposed to angular-leaf spot infection 



PLANTS ATTACKED 



hor- 



Cucumber {Cucumis sativus), 

 ti cultural varieties: 



Davis Perfect. 



Chicago Pickling. 



Boston Forcing. 



Early Russian. 



Giant Pera. 



Japanese Climbing. 



Heinz Muscatine. 



Lemon. 



Thorbum's Everbearing. 



Rollison's Telegraph. 



Vaughan 's Prolific Forcing. 



White Spine Klondyke. 

 West Indian gherkin {Cucumis an 



guria). 

 Mandera gourd (Cucumis acutangulis) 

 Hedgehog gourd {Cucumis dipsaceus). 

 Calabash gourd {Ljigenaria vulgaris). 



PLANTS NOT ATTACKED 



1. Balsam-apple {Momordica balsamina). 



2. Balsam-pear {Momordica charantia). 



3. Squirting cucumber (Momordica ela- 

 terium). 



4. Pomegranate melon (Cucumis melo var. 

 dudaim) . 



5. Cucum^is grossulariaeformis. 



6. Muskmelon (Cucumis melo), 11 va- 

 rieties. (^ 



7. Snake melon (Cucumis melo var. flex- 

 uosus) . 



8. Wild cucumber (Echinocystis lobata) . & 



9. Watermelon (Citrullus vulgaris), 2 

 varieties. <^ 



10. Citron (Citrullus vulgaris). 



11. Japanese crookneck squash (Cucur- 

 bita Tnoschata). 



12. Hubbard squash (Cucurbiia maxima). « 



13. Turban squash (Cucurbita maxima). 



14. Summer squash (Cucurbita pepo var. 

 condensa). 



15. Pumpkin (Cucurbita pepo)."- 



16. Gourd (Cucurbita pepo var. ovifera). 



17. Trichosanthes colubrina. 



In the case of the plants other than cucumber attacked the causal 

 organism was isolated from diseased spots and identified by inoculating 

 cucumbers. Stained sections from paraffin-embedded matetial showed 

 bacteria within the tissue of the leafspots in all cases except that of the 

 West Indian gherkin, which was unquestionably subject to the disease. 



STOMATAIy MOVEMENT AND INFECTION 



The fact that leaf infection took place through the stomata was re- 

 ported by Smith and Bryan {15, p. 469), but th^ gave no discussion of 

 the conditions necessary for infection. Practicafly all of the earlier in- 

 oculations made by the writer were performed in the evening, after dark, 



a Greenhouse Inoculations aiso gave negative results. 



b The wild cucumber plants were not in t&e experimental plots, but grew near by and were artificially 

 inoculated. 



6. Bryanopsis laciniosa. 



