PROTOZOA OF LATEX PLANTS 275 



of the uninfected specimens. This method, however, succeeded 

 no better than the others. 



Further work is needed, for it may prove possible to devise 

 methods of reducing the pressure of the latex in the uninfected 

 plants within the latex cells, or of reducing the pressure of neigh- 

 boring cells, or of preventing the coagulation of the latex in the 

 wound, thus facilitating mechanical transfer of latex flagellates 

 from plant to plant. 



Other problems. The problems above outlined are those which 

 have been suggested by earlier work. As information is accumu- 

 lated in this field other points will suggest themselves. Study of 

 insect hosts concerned in the transmission of known flagellates 

 may indicate in which insect groups the carriers of other species 

 may be expected to occur. Study of plant hosts of latex flagellates 

 may lead to generalizations as to which genera and species are 

 capable of becoming infected when in the presence of suitable in- 

 sects. Some latex plants have never been found infected. This may 

 indicate that their latex is an unfavorable medium for the growth 

 of flagellates. It is not yet known whether flagellates of this group 

 can pass from insect to insect without the intermediate step in 

 latex. The testing of new plants as commercial sources of rubber 

 will furnish large numbers of problems in this field of the study 

 of the herpetomonad flagellates capable of living in the latex of 

 plants. 



