DESCRIPTION OF PLATES. 



Fkontispiece. — Turnip plant Xo. 53, showing place of inoculation (on leaves) and 

 indicating by tigures the part oi root from which sections were taken 

 for the photomicrographs. Diagrammatic. The illustrations were all 

 made from the root of plant No. 53, except fig. 1, PI. I, from another 

 turnip, and fig. 0, PI. VI. which was made from a cabbage plant attacked 

 by the same disea.se. 



Plate I. Fig. 1. — Cross section of turniji plant, showing bacterial cavity. Natural 

 infection. From a fiel<l near Baltimore. Zeiss planar, x 4h circa. 

 Fig. 2. — Single vessel from PI. II, showing bacterial occui)ation. Stained 

 with nigrosin. x 2000. 

 II. Cross section of lower part of the root (Frontispiece, 3), differentially 

 stained with safranin and picro-nigrosin to bring out location of the 

 bacteria, x 50. 



III. Cross section of a part of the middle portion of the root (Frontispiece, 2), 



differentially stained with carlwl fuchsin, showing numerous bacterial 

 cavities, x 15. 



IV. Fig. 1. — Cross section, extreme upper portion of the root ( Frontispiece at 



point marked 1 1, differentially stained. Zeiss, TO mm. x 23. Fig. 2. — 

 Detail from the same section (at X) more highly magnified. Zeiss, 

 16 mm. X 185. 

 Y. Fig. 1. — Longitudinal section in middle of root (Frontispiece, 2) showing 

 reticulated vessels filled with the bacteria and surrounding tissue free 

 from infection, x 154. Fig. 2. — Longitudinal section from same level as 

 Fig. 1, showing vessels filled witli the Fseudomonas, and a cavity around 

 the upper bundle, x 136. 

 YI. Fig. 1. — Cross section, middle of root, differentially stained, showing a 

 single ves.«el packed with the bacteria. This may be compared with 

 fig. 1, PI. Y. X 520. Fig. 2. — Cross section from same portion of the 

 root differentiallv stained, showing a small bundle partly occupied by 

 the Piii'mloiKOwiL The larger vessel contains <;)nly a rim of bacteria. 

 The surrounding tissue is free from bacteria, x 460. Fig. 3. — Cro.«s sec- 

 tion, middle of' root, differentially stained, showing vessels and non- 

 lignified wood parenchyma occupied by the bacteria. In the middle 

 portion the cells have begun to disorganize and a bacterial cavity is in 

 process of formation, x 385. Figs. 4 and 5.— Bacteria separating cell 

 walls. X 1000. Fig. 6. — Ps. camphtris. Smear preparation from a cab- 

 bage stem, stained with carbol fuchsin. k 1000. 

 YII. Figs. 1 and 2. — Cross sections, middle of root, differentially stained, show- 

 ing small bundles verv fullv occupied bv the Fseudomonas. Fig. 1 x 475. 

 Fig. 2 X -170. 



VIII. Fig. 1.— Cross section, middle of root, differentially stained, showing par- 

 enchvma cells with bacteria multiplying in their intercellular spaces. 

 The cell cavities are free, x 1000. Fig. 2.— Cross section, middle of 

 root, differentiallv stained, showing disorganization of a small bundle. 

 X 1000. 

 IX. Fio's. 1 and 2. — Cross sections, middle of root, differentially stained, show- 

 fng formation of liacterial cavities. Zeiss apochromatic 3 mm. oil immer- 

 sion ol)jective 1.40 X. A. and compensating ocular Xo. 4. Cramer's slow 

 isochromatic plates, Zettnow's color screen, with sunlight, x 1000. 

 X. Figs. 1 and 2. — Cross sections, mid<lle of root, differentially stained, show- 

 mg well developed, small cavities filled with the Psenfloiiionas and with 

 remnants of the disorganized cells, the latter conspicuous only on the 

 margins of the cavitv. x 340. 

 XI. Figs. 1 and 2.— Cross sectii ns. middle of root, differentially stained, show- 

 fng margins of cavities with cell walls in all stages of solution, x 1000. 

 XII. Fig. 1. — Radial longitudinal section, middle of root, differentially stained, 

 showing one large cavitv and several small ones. Bark part of root at 

 right-hand side, x 85. "Fig. 2.— Detail from upper left-hand corner (X) 

 of fig. 1. X 475. 



XIII. Details from fig. 1, PI. XII, showing vaiious stages in the separation and 

 solution of cell walls. Fis:. 1 is from XII. 1. Y. Fig. 2 is from XII, 1, 

 Z. x475. 



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