192 



PYTHIUM DISEASE OF GINGEE, TOBACCO AND PAPAYA 



pointed, beak. The intercalar ones are knob-shaped and pointed. The oospores 

 are round, smooth, hyaline, thick-walled and measure 13-5 to 25- 3/* in 

 diameter. They lie loose in the oogonia and germinate by a germ-tube 



(PI. V, fig. 6). 



The fertilization is the same as described by Ward.* 



Systematic Position. 



None of the species described under the gracile group comes very near 

 to the present one, except the species studied by Butler and Ward2 and pro- 

 visionally put under Pythium gracile Schenk. However, this species differs 

 in not being an algal parasite. Several inoculations on Spirogyra and 

 Cladophora gave negative results. 



From Pythiiim monospermum Prings. (P. gracile de Bary, P. coinplens 

 Fischer), it differs sharply in the oospore lying quite loose in the oogonium 

 (which may be twice the diameter of the oogonium of P. monospermum), and 

 in the antheridia and oogonia usually arising from different branches and not 



1 Ward, H. M. " Observations on the genus Pythium (Prings.)." Quarterly Journal of 

 Microscopical Science, n. s., XXIII, 1883. 



2 Ibid. 



