156 THE NORTH AMERICAN SLIME-MOULDS 



the capillitium of a stemonitis. These ascending branches are in 

 many cases, probably in all, real, though as yet imperfectly developed, 

 columellae. They rise, at least in many cases, directly from the hypo- 

 thallus, each is central to an individual sporangium, rises to about 

 two-thirds its height, but never attains the summit. The sporangia 

 are so crowded that many are choked off below, never reach the top 

 of the aethalium. In such cases the columella may cease at the spo- 

 rangium-top. The columella bears cystiferous threads sparingly, if at 

 all; nevertheless these abound in the peripheral portions of the spo- 

 rangium all the way up, and are especially noticeable beyond the 

 level of the top of the columella. Many are so arranged that the 

 plexus with its vesicles occupies a place in the plane separating adja- 

 cent sporangia, suggesting the possibility that we have here to do 

 with an imperfectly developed surface-net and peridium. In this 

 view the cysts would represent the meeting-point of two opposite 

 radial capillitial threads rather than the middle of one. This accords 

 with Rostafinski's observations and drawings. The cysts, then, be- 

 long morphologically to the peridium or sporangium wall. It is a 

 stemonitis whose sporangia have never been perfectly differentiated, 

 a case of arrested development. See further under Stemonitis 

 confluens. 



Rostafinski really offers the first definitive description. P'ries prob- 

 ably distinguished it, but his description would not indicate the fact 

 except for the added note wherein appears the reason for discarding 

 an apparently older name, viz., that given by Link. But neither 

 Link nor Sowerby distinguished by description or figure Brefeldia 

 from Amaurochaete. 



Throughout the northern forest; Maine to Vancouver Island: not 

 common. 



2. Stemonitis (Gleditsch) Rost. 



1753. Stemonitis Gleditsch, in part, Meth. Fung., p. 140. 

 1873. Stemonitis (Gleditsch) Rost, Versuch, p. 7. 



Sporangia distinct, though often closely aggregate, cylindric, stipi- 

 tate; columella prominent; capillitium well developed by repeated 

 lateral and apical branching of the columella, at length assuming at 

 the surface the form of a distinct net which supports an evanescent 

 peridium. 



