conspectus: reaction of the plant 49 



ference after more than two months. See also Fig. 169 where 

 the development of the potato shoot inoculated with Bacillus 

 carotovorus has lagged behind its twin shoot. Even more 

 striking retardation results were obtained by the writer and 

 Mr. Godfrey (summer of 1918) on Ricinus communis and 

 on Helianthus annuus, using the same organism (Figs. 127, 131). 

 On potato plants attacked early by Bacterium solanacearum 

 the tubers remain small. On maize attacked by Aplanohacter 

 stewarti the ears are imperfect. Olive shoots inoculated and 

 infected by Bacterium savastanoi are always dwarfed (Figs. 

 299 and 300), and frequently the crown-gall dwarfings are very 

 conspicuous. The dwarfings of melon and squash plants at- 

 tacked by Bacillus tracheiphilus are also conspicuous. Unin- 

 oculated sugar-cane stems soon surpass in height and vigor 

 those successfully inoculated with Bacterium vascularum. I 

 do not know how to explain this checked growth unless it be 

 due to the paralyzing effect of absorbed toxins. 



Changes in color are also conspicuous. The attacked parts 

 may become greener than normal, or fade to yellow, red, brown 

 or black. In tomato fruits there is often a retarded ripening 

 on the attacked side, with persistence of the chlorophyll. 

 In certain leaf-spots also the leaf green persists in the vicinity 

 of the spot while the rest of the leaf becomes yellow (bean- 

 blight). Crown galls on daisy are greenish. On the contrary 

 the teratoid parts of crown galls on tobacco and on cauliflower 

 are often blanched. The male inflorescence of maize attacked 

 by Aplanohacter stewarti ripens prematurely and becomes white 

 (Fig. 101). 



Distortions of various kinds appear (leaves of bean, lilac, 

 larkspur, hyacinth, mulberry, Persian walnut, etc.). The leaves 

 of tomato plants attacked by Bacterium solanacearum are bent 

 dow^nward; so are the fronds of the coconut palm when at- 

 tacked by the bacterial bud-rot (Fig. 4). The leaves of potatoes 

 attacked by Bacillus phytophthorus are sometimes bent upward 

 and almost always the leaflets are rolled upward, from the 

 edges. Knee-shaped curvatures of the culms appear on 

 Dactylis attacked by Aplanohacter rathayi, in the buds of the 

 sugar-cane attacked by Cobb's disease, on Agropyron attacked 



