314 Agricultural Experiment Station, Ithaca, N. Y. 



number of kidney-sliaped masses, with two lateral cilia according to 

 most authors, although Ilesse,^ who first described the process in this 

 species, says that the zoospores are oval and uniciliate. These 

 swarm about in the water for a few minutes, come to rest, round off 

 and germinate in the ordinary way for conidia by sending out a 

 slender germ tube which when favorably situated will start the 

 disease in fresh plants. It is probably by the development of these 

 in wet soil during rain or at the time of watering the pots or soil in. 

 seed beds that the disease is spread so rapidly. 



The fungus is, however, capable of developing as asaprophyte on 

 dead or partially decayed organic matter in the soil so that with one 

 w^atering it may become well seated in nearly all parts of the bed. 

 To show that it is also a saprophyte it is a very easy matter to start 

 it in the laboratory on the leaves or stems of seedlings which have 

 been previously killed by boiling. 



This damping-off fungus was first described by Hesse in 1874: 

 (1. c.) and named by him Pythium debaryanum. It was shown 

 by him to be a parasite of seedlings, such as Camelina sativa, Tri- 

 folhim repens^ Spergula arvensis, Panicum Tniliaceum and Zea. 

 mays, while seedlings of Solanum tuherosum, Linum usitatissi- 

 Tnum, Papaver somniferum, Brassica napiis, ornithopus sativuSy 

 OnobrycTiis, Pisum, Hoi'deum mdgare, Triticum vulgare and 

 Avena sativa were not attacked. 



DeBary made a comprehensive study of the sexual stage. ^ 

 Pythium equiseti Sadebeck, is in his opinion the same species^ 

 P. equiseti was ^rst described by Sadebeck " in 1874 from prothallia 

 of Equisetum arvense, and in farther studies ''' it was shown that not 

 only did it occur in potatoes affected with Phyfophtkora infes- 

 tans ^ but that healthy potatoes could be inoculated with it. 

 Pythium autumnale Sadebeck which grew in young plants of 

 Equisetum palustre and £. Ihnosum, produces oospores which 



* Hesse, Pythium (lebaryannm, eiu entophytischer schniarotzer, Halle, 1874, 



SBeitr. z. Morph. u. Pbys. <l. Pilze, IV, 1881. 



^Ueber eineu tier faiiiilie der Saproleguiaceeii augeliorigeu Pilze in deru pro- 

 thallien des Ackerschachtelhalmes. Sitzuugsb. d. Bot. Ver d. Prov. Bran- 

 dcnberg, 116-122, 1874. 



■? Neue Untersnchuugeu iiber Pythium equiseti. Sitsungsb. d. Gesells. 

 naturf. Freunde z. Berlin, V, 21, 1»^75. 



8 Ueber Infectionen welche Pythium-Arten bei labenden Pflanzen hervor- 

 bringen, Beibl. z. Tageb. d. 49 Vers, dentscber naturt". n. Aertze. 100, 1876^ 



