194 AIDS TO BACTERIOLOGY 



B. solanacearum affects members of the Solanacece 

 (tomato, egg-plant, and potato), producing discoloration 

 of shoots, stem, and leaves (brown rot). The fruit and 

 tubers are attacked also. B. solanacearum rots the skins, 

 and then, assisted by other bacteria and fungi, rots the 

 centres too. The Colorado potato beetle is sometimes 

 the traumatic agent, and can spread the disease. Cucur- 

 bitaceous plants are immune. The organism grows on 

 ordinary culture media, forming a yellowish-brown 

 pigment. 



B. tracheiphilus produces a wilting of the leaves (wilt 

 disease) in cucumbers, pumpkins, and other cucur- 

 bitaceous plants, but does not affect solanaceous ones 

 It forms a white viscid growth on agar, does not affect 

 milk, and produces acid in glucose and saccharose. 



B. amylovorus produces brov/ning and death (pear 

 blight) in the twigs of pear-trees. Peritrichally-arranged 

 flagella are present, and the organism is motile. A tur- 

 bidity is produced in broth, with formation of a pellicle. 

 Transmission is effected by bees. 



B. olese produces nodular formations on the olive 

 (olive-knot disease). B. hyacinthi causes the yellow 

 disease of hyacinths. 



Pseudomonas destructans, a short rod, with a single 

 terminal flagellum, causes ' white rot ' in turnips. Several 

 bacterial diseases occur in the cultivated potato viz., 

 Micrococcus nuclei, M. imperatoris, M. pellucidus, al- 

 ways found associated with the ' scab,' M. albidus and 

 M. flavidus. 



Penicillium glaucum most commonly causes the rotting 

 of fruits. In apples and pears this is accompanied by 

 Mucor pyriformis, and in the case of medlars the latter 

 is much the most common fungus. In lemons, oranges, 

 and other tropical and subtropical fruits, P. glaucum is 

 associated with two other closely-allied species, P. italicum 

 and olivaceum. In plums Mucor racemosus has been 

 observed. In grapes P. glaucum, and Botrytis cinerea are 

 the most common fungi. The latter species forms the 

 grey tufts on walnuts. 



B. tumefaciens is the primary cause of many of the 

 tumour-like growths on the roots of plants (crown gall). 



Gum-producing Bacteria. Greig Smith and Edie have 

 practically established as a fact_the_bacterial origin of 



