54 A Motwr/j-ajyh of the Mi/x<>(faf?tres. 



diameter, chestnut-brown, pruinose ; mass of spores and sup- 

 porting threads yellowish brown. 



Dictijdiathaliu.m dissilicns, Hazl., Just, Bot. Jahresb., 1877, 

 p. 156 ; Sacc., Syll, Vol. vii., pt. I, n. 1398. 



Hazlinsky states the present species, when ripe, dehisces in 

 an elastic manner on the slightest touch, brought about by 

 the sudden expansion of the elaters (= threads supporting 

 apical portion of sporangium) which in(n'ease to three times 

 their previous length. 



Cribraria. Pers. (emended). 



Wall of sporangium single, with thickened permanent portions 

 arranged in the form of more or less parallel ribs at the base, 

 branching and anastomosing above to form an irregular net- 

 work, angles of network sometimes dilated and enclosing 

 granules; thin portions of wall entirely disappearing at ma- 

 turity, or the basal portions between the radiating ribs per- 

 sistent and forming an imperforate calyculus ; columella and 

 capillitium absent. 



Cribraria, Pers. Syn., p. 192 ; Rost., Mon., p. 57 ; Cooke, 

 Myx. Brit, p. 57; Schroeter, p. 104; Zopf, p. 141; Sacc, SylL, 

 Vol. vii., pt. I., p. 412. 



Hderodidyon, Rost., Mon., p. 231 ; Cooke, Brit. Myx., p. 57 ; 

 Sacc, Syll., p. 411. 



After a careful comparison of specimens or figures of all the 

 species, with two exceptions, I find it impossible to retain 

 Rostafinski's genus Hderodictyon. In Cribraria we find, as 

 a rule, a calyculus at the base of the sporangium, composed 

 of more or less parallel ribs, with the thinner intermediate 

 portions persistent ; from the irregular margin of the calyculus, 

 the upper network commences, or rather, may be looked upon 

 as a continuation of the ribs of the calyculus; if the upper 

 portion starts from the margin of the calyculus, as an irregular 

 net-work consisting of well-defined nodes united by thin 

 strands, it represents Rostafinski's conception of Cribraria; 

 but if the lower portion of the network consists of more or 

 less parallel, broad ribs, joined laterally by thin strands, and 



