VIII Journal of Agricultural Research voi. iv 



PSEUDOMONAS CiTRI, THE CaUSE OF CiTRUS CaNKER 



Page 

 Plate IX. Pseudornonas ciiri: Fig. i. — Drawing of a stained section of a portion 



of a grapefruit leaf bearing a young canker resulting from inoculation with 

 a pure culture of P. citri. Fig. 2. — Photomicrograph of P. citri stained by 

 the Williams method for flagella. Fig. 3. — Top view of a grapefruit seedling 

 showing the results of artificial inoculation with P. citri isolated from Texas 

 specimens. Fig. 4. — View of the lower side of the leaves shown in figure 3. 

 Fig. 5. — Top view of a grapefruit seedling showing the results of inocula- 

 tion with P. citri obtained from Florida specimens. Fig. 6. — View of the 



lower side of the leaves shown in figure 5 ico 



Plate X. Pseudomonas citri: Small lesions on Citrus twigs and more obvious 

 cankers on Citrus leaves. A, Cankers on twig and leaves from Florida 

 produced by natural infection; B, natural infections on leaves from Texas, 

 C, cankers on twig and leaves produced by artificial inoculation 100 



Wilt of Gipsy-Moth Caterph^lars 



Plate XI, " Wilted ' ' gipsy-moth caterpillars hanging to a tree trunk 128 



Plate XII. Fig. i. — Photomicrograph of a smear from a "wilted" gipsy-moth 

 caterpillar. Fig. 2. — Photomicrograph of polyhedra clustering around a 

 tracheal tube of a gipsy- motli caterpillar. Fig. 3. — Photomicrograph 

 showing various stages during the formation of polyhedra in tissue nuclei 

 of a gipsy-moth caterpillar 128 



Plate XIII. Fig. i. — A silkworm polyhedron, after Prowazek. Fig. 2. — Two 

 gipsy-moth caterpillar polyhedra adhering to each other. Fig. 3 to 10. — 

 Polyhedra of gipsy-moth caterpillar cracking to pieces. Fig. 11 to 18. — 

 Urate crj'stals of a gipsy-moth caterpillar. Fig. 19. — Polyhedron of a gipsy- 

 moth caterpillar stained, showing a dark central mass. Fig. 20. — Polyhe- 

 dron of a gipsy-moth caterpillar stained, showing refractive granules. 

 Fig. 21. — Chromatin lump in middle of pathological nucleus of a gipsy-moth 

 caterpillar. Fig. 22. — Iron haematoxylin showing stained polyhedra of a 

 gipsy-moth caterpillar in a nucleus. Fig. 23. — Giemsa's stain, showing un- 

 stained polyhedra of a gipsy-moth caterpillar in a nucleus and little gran- 

 ules. Fig. 24. — Fully formed polyhedra of a gipsy-moth caterpillar in a 

 nucleus. Fig. 25. — Nuclear membrane rupturing and allowing polyhedra 

 of a gipsy-moth caterpillar to escape 128 



Plate XIV. Fig. i and 2. — Normal blood corpuscles of the gipsy-moth cater- 

 pillar. Fig. 3 and 4. — "Mulberry" corpuscles of the gipsy-moth cater- 

 pillar. Fig. 5. — "Mulberry" corpuscle of the gipsy-motli caterpillar 

 crushed, showing nucleus. Fig. 6. — Blood corpuscle of the gipsy-moth 

 caterpillar, showing nucleus filled with polyhedra. Fig. 7 to 9. — Blood 

 corpuscles of the gipsy-moth caterpillar with phagocj'tized polyhedra. 

 Fig. 10. — Cytoplasmic-free pathological blood corpuscles of the gipsy-moth 

 caterpillar. Fig. 11 and 12. — Crystals found in gipsy-moth caterpillars 

 that died of the "other cause" 128 



Effect of Temperature on Germination and Growth of the Common 

 Potato-Scab Organism 



Plate XV. Fig. i. — Germinating gonidia of the potato-scab organism, agar 

 hanging-block, 3 hotirs' incubation at 35° C. Fig. 2. — Germinating gonidia 

 of the potato-scab organism, agar hanging-block, 5 hours' incubation at 

 35° C. Fig. 3. — Involution forms of the potato-scab organism on synthetic 

 agar from a i-month-old culture, stained witli carbol fuchsin. Fig. 4. — 

 Involution forms of the potato-scab organism on synthetic agar from a 

 i-month-old culture, stained with carbol fuchsin 134 



