82 



PHYSIOLOGICAL RELATIONS 



taken to prevent the access of any spores from other sources. 

 Ordinarily, precaution is fairly well secured by a sufficient number 

 of control plants. 



If the spores of a given fungus are obtainable in quantity, these 

 may be sprayed on the plant with an atomizer or small pump. A 



small number of spores may be 

 sponged on or applied with a 

 camel' s-hair brush. If the inoc- 

 ulations are made towards even- 

 ing, and the plants are wrapped 

 loosely with paper or cloth, a 

 moist condition may be readily 

 maintained for a period suffi- 

 ciently long. The cylindrical, 

 open-topped, glass, insect breed- 

 ing-cage is extremely useful as a 

 cover for inoculated herbaceous 

 plants of small size (Fig. 17). 

 The top may be closed with a 

 cloth, and thus ventilation is 

 well provided for, while the 

 moisture retained is usually 

 sufficient. It insures, also, pro- 

 tection against insects, but not 

 against wind-blown spores. Tall 

 bell glasses may be used when an atmosphere practically saturated 

 is not objectionable. In this case, moreover, a relatively favorable 

 state of humidity and aeration may be maintained by raising the 

 bell glass on blocks. To provide against accidental infection great 

 caution must be observed, as stated below. In the local inoculation 

 of a twig, glass tubing may be slipped over the inoculated branch ; 

 the ends of the tube may then be plugged first with moist and 

 afterwards dry cotton. Glass vessels so employed may usually be 

 removed within a few days. 



Bacteria and certain leaf spot and stem inhabiting fungi may 

 require wounding of the surfaces to which they are applied. The 

 wounds may be made either with sterile needles, scalpels, or scissors, 

 and the depth of such wounds must be determined by experience 



FIG. 17. INSECT BREEDING-CAGE IN 

 INOCULATION EXPERIMENTS 



