124 THE NORTH AMERICAN SLIME-MOULDS 



ulate, slender; hypothallus none; columella pale or white, turbinate, 

 globose or depressed-globose; capillitium of dull brown, or colorless 

 threads more or less branched, always white at the tips; spores viola- 

 ceous, nearly smooth, 7.5—8.5 [x. 



This seems to be the most common form in the United States. It 

 is distinguished from the preceding by the longer, more delicate, gen- 

 erally orange-yellow, stem with pale or white columella. The spores 

 also average a shade larger. N. A. F., 412 and 2089, are illustra- 

 tions of D. xanthopus. The columella in blown-out specimens is 

 very striking, well confirming the diagnosis of Fries, "valde prom- 

 inensj globosa, stipitata, alba." Berkeley makes the color of the 

 capillitium diagnostic of D. proximum, but this feature is insufficient. 



Eastern United States; common. 



12. DiDYMIUM EXIMIUM Peek. 



Plate XVI., Figs. 11, 11 a, 11 ^'. 

 1879. Didymium eximium Peck, Rep. N. Y. Mus., XXXI., p. 41. 



Sporangia scattered, dull grayish-yellow or gray, depressed-globose, 

 umbilicate, minute, stipitate; the peridium comparatively thick, tena- 

 cious, especially persistent below, tawny or yellow; the stipe pale 

 brown or orange, erect, even or slightly enlarged at base ; hypothallus 

 scant or none; columella prominent, more or less discoidal, rough, or 

 spinulose, especially on the upper surface, yellow; capillitium not 

 abundant, pale fuliginous, often branching and anastomosing so as to 

 form a loose net; spores nearly smooth, dark violaceous by trans- 

 mitted light, 8.5-9.5 IX. 



The species differs from D. xanthopus in several particulars, — in 

 the much firmer, more persistent, and less calcareous peridium, in the 

 more complex capillitium, in the darker and larger spores, and espe- 

 cially in the peculiar and prominent columella, which is not only, 

 rough, but even "sometimes spinulose even to the extent of long 

 spicules penetrating to one-third the height of the sporangia." N. A. 

 F., 2493. 



As stated under No. 8, these last two species are called varieties 

 only of D. nigripes. They are so retained in Mycetozoa, 2nd ed. 



