[Vol. 2 



392 ANNALS OF THE MISSOURI L50TANICAL GARDEN 



MORPHOLOGY AND CULTURAL CHARACTERS OF THE PARASITES 



Most of the plant bacteria are small or medium sized rod- 

 shaped organisms. Very few parasitic coccus forms are 

 known. In fact, none are very well established. Some of 

 these bacteria are Gram positive, others are not. All take 

 stains, especially the basic anilin dyes, but not all stain with 

 the same dye or equally well. Most of the species are motile 

 by means of flagella — polar or peritrichiate. A few are non- 

 motile, genus Aplanobacter. 1 Some develop conspicuous cap- 

 sules, others do not. Few, if any, produce endospores. 

 Grown pure on culture media in mass, they are either yellow, 

 pure white, or brownish or greenish from the liberation of 

 pigments. Red or purple parasites are not known. We for- 

 merly supposed that there were no green fluorescent species 

 capable of parasitism, but now several are known, e. g., the 

 organism causing the lilac blight of Holland, with pure cul- 

 tures of which the writer obtained typical infections at 

 Amsterdam in 1906, and afterwards in the United States 

 (now first recorded). Some species produce gas, liquefy 

 gelatin, consume asparagin, destroy starch, and reduce ni- 

 trates ; others do not. Their fondness for sugars and alcohols 

 is quite variable. Some are extremely sensitive to sunlight 

 and dry air (Bacillus carotovorus, Bacillus tracheiphilus). 

 Others are remarkably resistant, remaining alive and infec- 

 tious on dry seeds for a year (Bacterium campestre, Bac- 

 terium Stewarti, Aplanobacter Rathayi). Some are strictly 

 aerobic, others can grow in the absence of air, if proper foods 

 are available. Some are very sensitive to acids, alkalies and 

 sodium chlorid, others are not. Some have wide ranges of 

 growth from 0°C. upwards. Some will not grow at or near 

 0°C, others will grow at or above 40° C. Very few, however, 

 will grow at blood temperature, certain ones even in plants 

 or on culture media are killed by summer temperatures, and 

 none are known definitely to be animal parasites. 



1 Smith, E. F. Bacteria in relation to plant diseases. Carnegie Inst. Wash- 

 ington. Publ. 27 1 : p. 171. 1905; Ibid. 27 8 : pp. 155, 161. 1914. 



