350 



BACTERIA IN RELATION TO PLANT DISEASES. 



gelatins. Cane-sugar added to the gelatin favors long continued growth, especially if the 

 medium is quite alkaline on the start. 



Minimum temperature for growth approximately 4 C. ; optimum temperature 28 to 

 30 C. ; maximum temperature approximately 34 to 35 C. Bact. hyacinthi will not grow 

 in the thermostat at 37 C., and grows very feebly on some media and not at all on others at 

 34 to 35 C. Thermal death point 47.50 C., most of the rods are killed at 46.50 C. 



Good media for long continued growth are litmus-milk, sugar-beet cylinders in water, 

 and nutrient gelatin neutralized to phenolphthalein with sodium hydrate and then acidified 

 with malic acid ( + 50) and dosed with 5 per cent cane-sugar. The vitality on culture- 

 media (except at high temperatures) usually varies from 3 or 4 weeks to as many months, 

 156 days and 174 days being the oldest viable cultures observed; these vigorous old cul- 

 tures were on 30 gelatin, and on o gelatin with 10 per cent cane-sugar and malic acid to 

 read +54 of Fuller's scale, the temperature ranging from 10 to 25 C. 

 The slow development of the parasite in the host plant is attributed 

 to its feeble action on cell-walls, its feeble action on starch, its sensi- 

 tiveness to acids, and its strict aerobism. 



RESUME OF SALIENT CHARACTERS. 

 POSITIVE. 



Pathogenic to Hyacinthus orientalis causing a yellow disease of 

 the vascular system and finally a decay of the bulbs ; a short motile 

 rod, single, in pairs or 4's end to end, with rounded ends and one polar 

 flagellum (chains and filaments in sugar-rich media) ; pseudo-zoogloeae 

 and involution forms; stains readily from young cultures in basic 

 anilin dyes; bright yellow in the host plant and on media; a slow 

 grower; surface colonies flat, roundish, smooth, wet-shining; aerobic; 

 inverts cane-sugar; slowly liquefies nutrient gelatin and Loeffler's soli- 

 dified blood-serum; liquefaction of gelatin prevented by addition of 

 cane-sugar in sufficient quantity; dissolves middle lamella in hyacinth, 

 and softens it in turnip and carrot, but only very slowly; produces a 

 non-volatile acid in small quantities from grape-sugar, fruit-sugar and 

 cane-sugar, and a volatile acid and probably also an ester (steam 

 fragrant) from ethyl alcohol; grows well in milk, forming a bright 

 yellow rim and tyrosin crystals, leucin ( ?) ; blues litmus milk, pre- 

 cipitating the casein (by means of a lab ferment) as a mobile fluid 

 which settles slowly and becomes partially peptonized tyrosin crystals appear slowly; 

 growth on potato-cylinders not long continued nor very copious (iodine-starch-reaction 

 always present, i. e., diastasic action feeble); tolerates sodium hydrate to beyond 20 

 on Fuller's scale, also tolerates malic acid in beef-bouillon to about +30 and lactic 

 acid to about +40; growth very slow on nutrient starch-jelly, much improved by addition 

 of diastase; growth retarded by glycerin and by large doses of grape-sugar (9 per cent), 

 or cane-sugar (17 per cent); streaks on the sugar-agars (9 to 23 per cent) were dry (not 

 syrupy) and were variously areolated, reticulated, wrinkled or shagreened; growth feeble 

 in Uschinsky's solution, better with peptone added; dextrin stimulates growth; sensitive 

 to sodium chloride and to acids, e. g., lactic, oxalic, acids of gelatin, growth retarded in 

 hyacinth-juice and in other acid plant-juices; grows slowly and with much difficulty in 

 bouillon over chloroform; moderate development of hydrogen sulphide; reduces litmus 

 slowly; methylene blue in Dunham's solution reduced, final color bright blue; indigo- 

 carmine in Dunham's solution becomes bright blue; rosolic acid in Dunham's solution 

 becomes colorless and the bacterial precipitate is stained; acid fuchsin in Dunham's 



Fig. 148.* 



*Fic. 148. Shagreen surface of Bact. hyacinthi on slant agar containing much cane-sugar. 



