JONES' SOFT ROT OF CARROT, ETC.: TECHNIC 243 



be done either in the laboratory or in the hothouse. Owing to 

 the rapidity of the rot, it lends itself very well to laboratory 

 experiments, as the various susceptible organs can be inoculated 

 and the results obtained before the plants begin to shrivel from 

 exposure to unsuitable laboratory conditions. If whole roots are 

 used, such as carrots, radishes and turnips, they may be exposed 

 after inoculation either to the dry air of the room or may be 

 put into deep uncovered jars. These latter serve better than the 

 open air of the laboratory to hasten the earlier stages of the 

 infection, but are not required to induce it. Full-grown or 

 nearly full-grown roots are better for inoculation than immature 

 ones. Such roots must not be flabby. 



As additional materials for inoculation, the student may 

 use green cucumber fruits, which rot quickly, or green tomato 

 fruits. He may also try the white, fleshy, central part of cab- 

 bage stumps. 



By far the most convenient w r ay, owing to the small space 

 required, is to make the inoculations on thick slices of uncooked 

 roots and fruits placed in deep, covered Petri dishes holding 

 part of the slices in each dish uninoculated for comparison. 

 For preparation of these slices which may be 2 to 3 centimeters 

 thick, see Part II, page 103. 



Determine 



FOR THE ORGANISM. Morphology. - - Size in microns 

 (especially the diameter of the rods, most of which should 

 measure 0.7 to 0.8^). Absence of endospores (try heat and 

 spore stains). Absence of capsules. Motility on the margin 

 of a hanging drop (examine various cultures, old and young). 

 Number and location of the flagella (Lowit's flagella stain, 

 van Ermengem's stain). Occurrence of chains and filaments 

 (examine second-day bouillon and agar cultures). Measure 

 the longest filaments seen. Determine number of elements in 

 the longest chains. Are the filaments and chains always, or 

 usually, motile? Do pseudo-zoogloeae occur and, if so, in what 

 media and under what conditions? Staining properties (using 

 various basic anilin stains with and without mordants). Does 



