244 BULLETIN 94. 



its wall, at one or more points, a slender tube which elongates 

 into a hypha exactly like those of the former mycelium. This 

 enters a young seedling when favorably situated, and stajts the 

 disease again. 



The conidia and zoospores are rarely developed so abundantly 

 in this species as are the oogonia. In my cultures during Jan. 

 and Feb. 1894-5 the oogonia were far more abundant and no zoo- 

 sporangia were observed. DeBary says that sometimes one may 

 search for weeks and even months and not find zoosporangia. I 

 have therefore not had as yet an opportunity of studying the for- 

 mation of the zoospores from the zoosporangia and cannot say 

 whether or not they agree with those of Artotrogus intermedius 

 (deBary), which will be described in the next paragraph. The 

 following account is therefore abbreviated from published descrip- 

 tions. 3 The zoosporangia are usually not to be differentiated from 

 the conidia until the time for the development of the zoospores. 

 They are either terminal or intercalary, and sometimes so much 

 of the protoplasm migrates into them during development from 

 the supporting hypha that this is emptied for a short distance 

 near the point where the wall separates the zoosporangium from 

 the contents of the hypha. They usually remain attached to the 

 supporting hypha and at the time of maturity, if placed in fresh 

 water containing oxygen, a short protuberance is developed on 

 one side at nearly right angles to the supporting hypha, which 

 grows to a very short tube of a varying length but always shorter 

 than the diameter of the zoosporangium. Into this tube the pro- 

 toplasm migrates and causes the end of the short tube to swell 

 out into a rounded vesicle of about the same diameter as that of 

 the zoosporangium, with a thin enclosing membrane. The pro- 

 toplasm now breaks up into a number of kidney shaped masses, 

 with two lateral cilia according to most authors, although Hesse 4 

 who first described the process in this species says that the zoo- 

 spores 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 



3 DeBary, Zur Kennt. d. Peronosporeen, Bot. Zeit. 39, 521, 1881, Beitr. z. 

 Morph. u. Phys. d. Pilze, IV, 1881. 



Schroeter, Pilze, in Engler u. Prantl, Naturl. Pflanzenfam. i, i 104. 



4 H23se, Pythiutn deb.aryanutn, ein entophytischerschmarotzer, Halle, 1874. 



