172 THE NORTH AMERICAN SLIME-MOULDS 



1 797, applied the name Dictydium to all Cribraria-X-fos, species in 

 which the calyculus was wanting. Fries follows this, Syst. ]\Iyc., 

 III., p. 164. Rostafinski, VersucJi, p. 5, Mon., p. 229, first correctly 

 limits the genus and separates it from Cribraria. 1873-75. 

 A single species is widely distributed throughout the world, 



i. DICTYDIUM CANCELLATUM (BatscJi) Macbr. 



PLATE I., Figs. 6, 6 a. 



1789. Mucor cancellatus Batsch, Elench. Fung., II., p. 131. 



1797. Dictydium umbilicatum Schrad., Nov. Gen. PL, p. n. 



1801. Cribraria cernua Pers., Syn., p. 189. 



1816. Dictydium cernuum Nees, Syst. d. Pilz., p. 117. 



1875. Dictydium cernuum (Pers.) Rost., Mon., p. 229. 



1893. Dictydium longipes Morgan, Cin. Soc.Jour., p. 17 (in part). 



Sporangia gregarious, depressed globose, nodding, the apex 

 at length umbilicate, stipitate, in color' brown, or brownish pur- 

 ple ; the stipe varying much in length from two to ten times the 

 diameter of the sporangium, attaining 5-6 mm., generally erect, 

 more or less twisted and pallid at the apex, below dark brown, 

 with hypothallus small or none ; calyculus often wanting, when 

 present a mere film connecting the ribs of the net ; the net made 

 up chiefly of meridional ribs connected at intervals by transverse 

 parallel threads, above an open Cribraria-\\k.Q network closing 

 the apex and more or less rudimentary; the spores varying 

 in color through all shades of brown and purple when seen in 

 mass, by transmitted light reddish, 5-7 ft, smooth or nearly so. 



This species in the United States is one of the most variable 

 in the whole group. The extremes of such variation might 

 easily constitute types for several distinct species were it not 

 that in all directions the varieties shade into each other so 

 completely as to defy definition. We have before us specimens 

 purple throughout and short-stemmed ; purple with stem long, 

 pale and twisted at the apex ; brown, with the same variations ; 

 short-stemmed, with the apex of the stem pallid, and long- 

 stemmed, with and without the same peculiarity. Morgan 

 (Cin. Soc. Nat. Hist. Jour., 1893) would set off the purple, long- 

 stemmed forms as D. longipes, " stipe three to five times the 



