322 



BACTERIAL DISEASES OF PLANTS 



(o-day potato cultures stained 10 minutes in Ziehl's carbol 

 fuchsin, then washed 1 minute in 70 per cent alcohol containing 

 3 per cent hydrochloric acid), non-sporiferous, motile, polar 

 flagellate (Fig. 248), feebly liquefying (gelatin and Loffler's 

 solidified blood serum), milk-curdling (by a lab ferment), 

 non-nitrate-reducing, starch-destroying, sunlight-sensitive (Fig. 

 249), dry-air sensitive, frost-sensitive in +15 bouillon (Fig. 250), 

 rod-shaped or short catenulate (2 to 4 or more elements) schizo- 

 mycete, growing on the surface of +15 agar-poured plates in 

 the form of round, thin, flat, smooth, wet-shining, very pale 

 yellow colonies which become a deeper color with age but are 

 still only pale yellow, i.e., distinctly paler than iYiOSQoi Bacterium 

 phaseoli, never deep yellow or orange colored. Well-grown 



Fig. 245. — Green cotton bolls attacked by Bacterium malvaceanun. Accidental, 

 hothouse infection. Washington, 1904. 



colonies on thin-sown plates measure 1 to 5 millimeters or more 

 in diameter. Early in their growth on +15 agar (second or 

 third day) the colonies are more or less radiate-mottled and 

 this is a good character for separating the parasite from yellow 

 cotton saprophytes which often accompany it or follow it 

 (Fig. 251 ) . The margin is thin and regular except in old colonies. 



10 spots — pedicel also involved; (2) another boll — photographed end on, showing 

 20 or more coalescing spots some of which involve the whole thickness of the 

 pericarp, as shown in Fig. 3 at X; (3) same boll as (2j but a side view with the peri- 

 carp split open to show the beginnings of the brown stain in the lint — base of the 

 pericarp also involved; (4) same as (3) but showing the opposite side of the boll — 

 lint at top stained brown. Inoculations of July 7, 1915, made with a "windowed" 

 c(}lony of the Arizona organism. The cotton Colletotrichum was not present in the 

 hothouse. Photographed by James F. Brewer. (See next page.) 



