290 



BACTERIAL DISEASES OF PLANTS 



on the plants it is necessary usually to wet down thoroughly the 

 interior of the cage and the earth under and around it in advance 

 of the inoculations. If moisture does not hold on the leaves they 

 must be sprayed again, and the earth wet down as before. 

 Watch carefully, for if the plants dry off speedily and remain 

 dry your experiment may not succeed. The plants should be 

 left in the cages only as long as necessary to secure numerous 

 infections. The writer does not know the minimum time. 



Fig. 224. — Bacterium phaseoli: A detail from Fig. 223, showing the bacteria 

 more distinctly. 



Perhaps you can determine it. He has had striking results from 

 26- and 30-hour exposures, equivalent to a dewy night followed 

 by a misty day. Probably a very considerably shorter period 

 of exposure would suffice. In default of cages, clean barrels 

 or boxes may be turned over the plants, or they may be cov- 

 ered with a tent-cloth or an oilcloth stretched over a frame. 

 Tent-cloths require very frequent wetting. 



King of the Garden (lima), Mexican tree bean. Green Flageo- 



