1915] 



SMITH BACTERIAL DISEASES OF PLANTS 



395 



have said, "With rare exceptions, the plant is passive or 

 nearly so," but that would have been a superficial obser 



In 



disease 



must suppose that the 



makes 



some effort to throw off the intruder, although often its forces 

 are paralyzed and overcome very early in the progress of the 



disease. 



One of the most conspicuous results is lessened growth. In 

 some of my plants recovering from brown rot due to Bac- 



Solan 



month aft 



signs of the 



disease had disappeared the check plants were twice the size 

 of the inoculated ones, and there was still a very decided dif- 

 ference after more than two months. I do not know how to 

 explain this checked growth unless it be the response to ab- 

 sorbed toxins. 

 On potato plants attacked early by Bacterium Solanacearum 



small. On maize attacked by Bacterium 



the tubers remain small. 

 Stewarti the ears are imperfect 



Olive shoots inoculated and 



infected by Bacterium S avast anoi are always dwarfed, and 



gall dwarfin 



frequently 



The 



dwarfing of melon and squash plants attacked by Bacillus 

 tracheiphilus is also conspicuous. Uninoculated sugar-cane 

 stems soon surpass in height and vigor those successfully in- 

 oculated with Bacterium vascularum. 



Changes in color 



The attacked parts 



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

 black. In tomato fruits there is often a retarded ripening 



persistence of the chlorophyll. 



In certain leaf 



on the attacked side with persi 



Crown-galls on daisy are greenish 



the leaf green persists in the vicinity of the spot 



rest of the leaf becomes yellow 



yellow (bean-leaf spot 

 of maize attacked by Bacterium St 



The male 



prematurely and becomes white 

 Distortions of various kinds 



of bean, lilac 

 The leaves oi 



larkspur, hyacinth, mulberry, Persian walnut) . The 



tomato plants attacked by Bacterium Solanacearum are bent 



downwards: so are the fronds of the coconut palm when 



1 Smith, E. F. 



Bacteria in relation to plant diseases. Carnegie Inst. Wash- 



ington : Publ. 27 s : pi. 45-D. 1914. 



