62 BULLETIN 934, U. S. DEPARTMENT OK AGRICULTURE. 



siana in pots of autoclaved soil which had received tap water at 

 Washington, D. C. It agreed both in the appearance and measure- 

 ments of its spiny oogones and smooth oospores with Pythium arto- 

 trogus (P. hydnosporus] as described and figured by Butler (23). 

 In addition to the spores which Butler describes, there appeared in 

 apparently pure prune-agar cultures of different strains bodies with 

 smooth walls, of somewhat irregular ovoid outline, and mostly larger 

 than either oospores or oogones. They are very much less abundant 

 than the sexual spore forms. Their greatest diameter varied from 

 11 \L to over 40 JJL. The germination of these bodies was not observed. 

 Efforts to induce the fungus to produce swarm spores by growing 

 them in liquid nutrient media and transferring them to pure water 

 were unsuccessful. This failure to produce zoospores is further in- 

 dication of the identity of the fungus with that described by Butler, 

 who says that asexual reproduction is unknown. 



The strain from Michigan was a rather weak growing organism, 

 difficult to maintain in tube cultures without rather frequent trans- 

 fers. Its parasitic activity in the experiments reported in Table VIII 

 is nil or negligible. Because of the poor seed and small number of 

 seedlings involved in experiment T2B, the percentage of damping- 

 off there given means only a single seedling dead. The Washington 

 strains, on the other hand, though evidently not strong parasites, did 

 apparently cause the death of a number of seedlings. The best evi- 

 dence of this is in experiment 68, in which there was damping-off 

 in each of the five 5-pot units containing the Washington strains and 

 none in any of the 18 control pots. The available strains were less 

 active not only than Pythium debaryanum^ but less than the Rheo- 

 sporangium and Phytophthora strains used. The fungus is be- 

 lieved to be a potential parasite on pine seedlings, but not one of an} T 

 general importance. What is probably the same fungus had ap- 

 peared in the writer's cultures from western nurseries in conjunc- 

 tion with P. debaryanum, but not commonly, and it had not been 

 isolated. While its growth rate is only about half that of P; debary- 

 anum on prune agar, it is nevertheless so much faster than that of 

 many fungi that it should have been more often obtained in culture 

 were it at all common in damped-off seedlings. 



Another fungus, presumably an oomycete but producing only 

 chlamydospores in the writer's cultures, was obtained from damped- 

 off olive seedlings furnished by Prof. W. T. Home and from soil 

 direct, both at Berkeley, Calif. The fungus is apparently the same 

 as one which has been occasionally seen in cultures from pine seed- 

 lings in the Middle West, but had not before been isolated. The 

 hyphse are ordinarily nonseptate, and the growth on corn-meal agar 

 is superficially much like that of Pythium debaryanum, but with 

 greater tendency toward local zonation and aerial growth and less 



