GENUS: PHYTOMONAS 



385 



tion and abnormal growth of the parasite, apparently as a result of ex- 

 haustion of nutriment. Amongst the degenerated parasites are some 

 forms of large dimensions. The latter may reach a length of 30 microns 

 and a breadth of 6 microns. The kinetoplast either entirely disappears 

 or becomes hypertrophied. This abnormal increase in size may be com- 

 parable with that of the giant forms of Herpetomonas fnirabilis and 

 H. tnesnili described above, and it may be that the presence of giant forms 

 in the fly and latex can be attributed to similar; disturbances of nutrition. 

 The effect of the infection on the latex has been mentioned. In a 

 section of a healthy leaf the lactiferous tubes are seen to be filled with 

 starch and other grains, whereas in an infected leaf the tubes are com- 



FiG. 182. — Plujtomonas davidi in a 

 Lactiferous Tube, as seen in a 

 Section of a Twig of Ewphorhia 

 segetalis. (After Franca, 1914.) 



Fig. 183. — Stenocephalus agilis ( $ ), the 

 Transmitter of Phytomonas davidi 

 in Portugal ( x 3). (After Franca, 

 1920, Modified.) 



pletely devoid of these (Fig. 182). Furthermore, the chlorophyll gradually 

 diminishes, and the plant finally withers and dies. Occasionally, however, 

 an infected twig will recover. 



Fran§a has also noted the flagellates in the sheath of the fruit, while 

 in the fruit itself he has seen minute bodies which, however, he cannot 

 certainly identify with the flagellates. He suggests the possibility of 

 their being forms destined to infect the seeds and bring about infection 

 of the young plants, a kind of hereditary infection analogous to the 

 supposed infection of the ova of insects. Strong (1924) has noted that 

 all parts of the plant, including the roots, may be infected. 



A transmitting host of the flagellate has been sought by several 

 observers. Lafont (1909) noted that the plants (E. hypericifolia) haj^- 

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