56 THE NORTH AMERICAN SLIME-MOULDS 



nioidcs Rost., /. c. Professor Sturgis, convinced that such reference 

 was at least doubtful, gave to our American gatherings the distinctive 

 name above, citing specimens from Massachusetts, from Colorado, and 

 from California. Curiously enough he also includes specimens of R. 

 didermoides var. lividum List., sent from England ! 



Rare! Certainly rare in Europe and so far seldom seen in the 

 United States, though widely distributed. Specimens are before us 

 from Ohio, Michigan, Iowa, Oregon. No doubt the mountains of 

 the north Pacific coast, a region to-day almost unsearched, will yet 

 afford the species in abundance. 



As stated Mr. Lister first applied the name P. diderma to a plas- 

 modiocarpous form occurring in England and near P. sinuosum. 

 More lately, Mon., 2nd ed., p. 78, he adopts a new specific name, P. 

 bitectum for the English specimens, and enters P. diderma as a prob- 

 able synonym for P. lividum R. Evidently our present form as de- 

 scribed above has not come to Mr. Lister's view. He says the 

 original type is not to be consulted. 



There is really no more merit in this later comparison than in that 

 discarded. The species P. diderma is not P. lividum, but stands as 

 originally delimited, and will, doubtless, some day yet again appear in 

 its own behalf upon the witness-stand of time; when, as before, a 

 Frenchman in DeBary's old-time haunts may rise to give it welcome, 

 brought back by some keen-eyed Polish student eager now in the arts 

 of peace, from Warsaw's shady groves. 



9. Physarum contextum Persoon. 



Plate IX., Figs. 3 and 3 a. 



1796. Diderma contextum Persoon, Ohs. Myc, I., p. 89. 

 1801. Physarum contextum Persoon, Syn. Meth., p. 168. 



thin inner one by an air-filled space; the calcareous nodules many, angular, 

 loosely developed within to form a pseudo-columella ; spores dark violet, 

 spinescent, 9.2-10 in diameter. 



"Opis. This physarum looks extremely like a diderma. 



"The sporangia stand either aggregated or bunched together in heaps of 

 five to twelve, adnate to the hypothallus by a narrow base, etc." 



Massee, Mon., p. 304, translated this description, but misunderstood what 

 is said of the columella and is inclined to think the author did not know a 

 diderma when he saw one; which is pretentious, to say the least! 



