522 DISEASES OF CULTIVATED PLANTS 



the formation of a gummy substance containing myriads of 

 bacteria. 



On cultivation, filaments olzLeptothrixform were observed, 

 the joints of which on separation showed mobile bacteria 

 075 to 1*25 [L in length. 



It is recommended to cut out all diseased parts, and protect 

 the wounds with gas-tar. But the safest method is to remove 

 and burn all diseased vines. 



Prillieux, Ed., Matad. des Plantes. Agric., i. p. 24 (1895). 



Root swellings of alder. Swellings on the roots of Alnus 

 incana and other species are well known. They vary in size 

 from a marble to that of a cricket-ball. In some cases the 

 swelling is a solid body with a tuberculose surface, suggesting 

 a mass of crowded, adventitious roots grown together except 

 at the extreme tips. In other instances, more especially 

 when the swellings are small, they are composed of root-like 

 outgrowths more or less free from each other. 



Waronin was the first to investigate these swellings, and 

 came to the conclusion that they were due to a fungus, which 

 he called Schinzia alni. 



Moller considered the organism present to be a myxomy- 

 cete, to which he gave the name of Plasmodiaphora alni. 



Brunchorst found a fungus in the swellings, which he 

 named Frankia subtilis. 



The last to investigate the subject was Bjorkenheim, who 

 observed fungus hyphae 3*5-4 //, thick, possessing a distinct 

 wall with a double contour, and distinctly septate. These 

 hyphae pass through the cell walls of the host, and often form 

 a dense convoluted mass, completely filling the cells. Fruit 

 unknown. 



Bjorkenheim, C. J., Zeit. Pflanzenkr^ 14, p. 130. 



Brunchorst, J., Unters aus dem Bot. Inst. zu Tubingen^ 2, 

 p. 151 (1886). 



Moller, Ber. d. deutsch. Bot. Ges., 3, p. 102. 



Woronin, Mem. Acad. Imp. St. Petersb., Ser. 7, vol. x., 

 No. 6. 



Bacterial knots. Zimmermann has announced the pre- 

 sence of small colonies of bacteria in living leaves of Pavetta 

 indica. These colonies are constantly present in the leaves 

 of this plant, and occupy the air cavities below the stomata, 

 a minute wart or knot on the surface of the leaf indicating 



