274 RESEARCH IN PROTOZOOLOGY 



The possibility of inoculating without the aid of insects. Another 

 problem which has not been settled is the question whether it is 

 possible to inoculate plants with the latex flagellates without the 

 aid of insects. Attempts have been made by introducing flagellates 

 in fine glass pipettes into the petioles and stems of uninfected 

 plants, and by dipping thread in infected latex and then pulling 

 this with a needle through uninfected plant parts. There have been 

 a few claims of success with these methods, although reports of 

 failures have been more numerous. The writer has tried in these 

 and other ways with Herpetomonas elmassiani in Asclepias species, 

 but has never obtained transfer of the flagellates to the uninfected 

 plants in spite of persistent attempts. 



Franga (1914) reported three successes in many trials, two 

 with the pipette method and one with the thread dipped in in- 

 fected latex. Noc and Stevenel (1911) also report successful trans- 

 fers in two cases. In none of the successful cases were the unin- 

 fected plants grown from seeds by the experimenters. Because of 

 this the possibility that infections existed but were not discovered 

 in examinations made before each experiment must be taken into 

 consideration. Rodhain and Bequaert (1911) report that two days 

 after attempts at transfer the flagellates swarmed in the experi- 

 mental plants. This seems to point to an earlier infection since the 

 result of insect infection studies would indicate that more than 

 a week would be required for an infection to become so general. 



The difliculties met in forcing latex flagellates into broken latex 

 cells of uninfected plants seem to be due to several factors, namely : 

 ( I ) The latex in the uninfected cells is under pressure and tends 

 to sweep infected latex away from the uninfected cells as it escapes 

 when a wound is made; (2) The latex of the uninfected cells 

 coagulates quickly, making the entrance into these cells mechani- 

 cally difficult; (3) The uninfected latex cells collapse because of 

 the pressure of neighboring cells when their own internal pressure 

 is reduced by the escape of latex, thus closing broken parts me- 

 chanically. 



The writer used a method of inarching, that is grafting by ap- 

 proach, an infected and an uninfected Asclepias nivea plant. After 

 the grafts were completed needle punctures were made through the 

 joined surfaces in the hope that infected latex cells of one plant 

 would be broken so near uninfected latex cells of the other that 

 latex of the infected plant would be forced into the latex cells 



