182 THE JOURNAL OF BOTANY 



Sporangia subglobose; stalks brown, short or absent, lime- 

 knots large and branching 



P. auriscalpium Cooke (11, p. 115). 



Stalk penetrating the sporangium for four-fifths its height 



£. Lime-knots white ; sporangia grey 

 * Stalk free from refuse matter 



P. penetrate Rex 



Stalk straw-coloured ; sporangium globose ; capillitium 

 with a central ball of lime . P. nucleatum Rex 



Stalk ochraceous, short or absent, sporangia ovoid or 

 cylindrical, with a long pseudo-columella 



P. Crateriachea List. (8, p. 323). 



Stalk straw-coloured, slender ; sporangia compressed ; 

 spores marked with patches of warts 



P. straminipes List. (12, p. 163"). 



Stalk red-brown ; sporangia globose, white 



P. calidris List. 



Stalk white, membranous, short or absent ; sporangia 

 ovoid or subglobose (and then sessile), without 

 pseudo-columella 



Spores very dark all over . P. didermoides Rost. 



Sporangia always sessile, spores paler on one side 

 P. didermoides var. lividum List. (12, p. 162). 



** Stalk containing refuse matter 



Stalk buff, black, or white ; sporangia subglobose ; 

 spores brownish violet . . • P. nutans Pers. 



Stalk black, buff, or white, stout; sporangia compressed, 

 often lobed ; spores dark purple-brown 



P. compressum Alb. & Schw. 



Stalk yellowish or dark, slender; sporangia compressed 

 and lobed, often clustered (smaller than P. com- 

 pressum, to which it is very nearly allied) 



P. Nicaraguense Macbr. 



B. Sporangia sessile, never stalked : 



a. Lime-knots white 



a. Sporangium-wall single 



Sporangia subglobose or forming plasmodiocarps white, or 



grey, spores pale brownish violet, 7-8 /x diam. 



P. cinereum Pers. 



Sporangia subglobose or forming plasmodiocarps white, or 

 grey, spores dark violet-brown, 9-11 /a diam. 



P. vernum Somm. (9, p. 210). 



Sporangia much compressed, forming rosettes or net-like 

 plasmodiocarps, lime-knots fusiform 



P. gyrosum Rost. (16, p. 210 ). 



Sporangia crowded, chestnut-brown 



p. Gnlielmae Penz. (24, p. 84). 



