246 BULLETIN 94. 



the description there is little doubt that it is the Artotrogus de- 

 baryanus. L. circumdans described by the same author in a fern 

 prothallium" develops only in the margin of the same, producing 

 short conidiophores and zoosporangia with 4-8 zoospores. Fis- 

 cher 12 also includes this with P. debaryanum Hesse, as well as the 

 Saprolegnia schachtii^ described by Frank in the thallus of the 

 liverwort Pellia epiphylla. Zoospores were not seen and oogonia 

 only rarely, the plant being usually sterile. 



A number of these are probably rightly referred to Artotrogus 

 debaryanus (Hesse). Unfortunately these plants cannot well be 

 preserved for study in their several stages and in most of the cases 

 probably no specimen of any stage has been preserved, so that it 

 would be quite impossible at the present time at least to speak 

 with any feeling of certainty on the proper disposition of these 

 forms. There is need of a thorough and comprehensive study of 

 the species of the genus, and considerable uncertainty will probably 

 exist as to the proper disposition of some of the above species 

 until they can again be found and critically studied. 



The fungus has been several times reported in this country, and 

 many notices of damping off have been made without, probably, 



" Ueber einige neue parasitische Pilze. Tagebl. d. 47 Vers. deutscher 

 Naturf. u. Aertze, 203, 1874. 



"Rabenhorst's Krypt. Flora, Pilze, IV, 404, 1892. 4 Ibid. 



*3 Notes on the fungus causing damping off, etc. Trans. Mass. Hort. Soc. 

 I. 1891. 



Explanation of Plate I. Artotrogus debaryanus (Hesse). 



Figs, i, 2 and 3, different stages in fertilization ; a antheridium, oog. oogon- 

 ium, e. c. egg cell, gon. gonoplasm, oosp. oospore. 



Figs. 4 and 5 intercalary oogonium with stalk antheridium (s. a) and 

 branch antheridium (b. a.), in 4 with gonoplasm separated from the peri- 

 plasm, and in 5 fertilization complete. 



Fig. 6 terminal oogonium with stalk and branch antheridium. 



Figs. 7 and 8 different stages in development, and fertilization, of sexual 

 organs ; b in 7, oogonium before the formation of the egg cell. 



Fig. 9 oogonium with stalk antheridium (a) which has fertilized the egg 

 cell, and branch antheridium (b) from another hypha than that which bears 

 the oogonium. In this branch antheridium the gonoplasm has separated, and 

 the fertilization tube has formed, but fertilization took place from the stalk 

 antheridium first and the wall of the oospore prevented the use of the 

 gonoplasm from the branch antheridium. 



All the figures drawn with aid of camera lucida and magnified 50 times more 

 than the scale. Scale i millimeter. 



