IO2 



BACTERIA IN RELATION TO PLANT DISEASES. 



an oil is driven off which otherwise would be deposited as a whitish distillate on 

 the inside of the test-tubes near the plugs. Hypodermic syringes may be sterilized 

 by boiling in distilled water if the contaminating organism is non-sporiferous, 

 or by soaking twenty-four hours in 5 per cent carbolic-acid water or lysol water and 



a subsequent soaking and boiling 

 in pure water. The writer prefers 

 the Meyer syringe, made by Lauten- 

 schlager (fig. 86). Syringes which 

 allow the culture media to ooze out 

 around the piston whenever any 

 strong pressure is exerted are danger- 

 ous and should never be used with 

 infectious material. Those which do 

 not admit light or allow the experi- 

 menter to see how much fluid has 

 been used or whether air is present 

 are unsatisfactory. In case of many 

 plants, needle-pricks are more satis- 

 factory than hypodermic injections 

 (pi. 4 and figs. 8 and 88). Needles 

 are sterilized in the open flame as 

 needed. 



When conveniences are not at 

 hand, as on long trips in the country, 

 the kitchen-oven may be used for 

 sterilizing glassware, or even an open 

 flame (alcohol lamp), and agar and 

 gelatin for the making of poured 

 plates may be melted by placing the 

 tubes in hot water in a tin cup or tea 

 kettle, but, in general, the writer has 

 not found the rooms of ordinary farm 

 houses very well suited for research 

 work. Usually they are too dusty. 



Surgeon's gauze is very conve- 

 nient for laboratory use, for coarse 

 filters, wipe-cloths, etc. 



Fig. 87.* 



*Fic. 87. Early stage in the infection of a cabbage leaf by Bacterium camfestre; a, epidermal 

 layer on the apical part of the tooth of a leaf, showing one of the four stomata ( X ) full of bacteria. 

 For the condition immediately under X see b, which was drawn from the third section in series, the 

 intermediate one including part of the guard-cells. 'Slide 338, Bi, stained with carbol-fuchsin. 

 Drawn with the Abbe camera, 3 mm. Zeiss apochromatic objective and 12 compensating ocular. 

 Material collected and fixed 8 days after infection, which was accomplished by atomizing upon the 

 plant water containing a pure culture of Bacterium campestrc grown on slant agar. When collected 

 many of the serratures had begun to show traces of the brown stain which invariably appears when 

 this organism grows in cabbage. The plant was inclosed in the cage shown in fig. 95, and was ex- 

 truding fluid from its water-pores when it was sprayed. X 500. 



