154 THE NORTH AMERICAN SLIME-MOULDS 



B. STEMONITACEiE 



Capillitium abundant, springing usually as dissipating branches 

 from all parts of the columella; the sporangia generally definite and 

 distinct, though sometimes closely placed and generally rising from a 

 common hypothallus. 



Key to the Genera of the Stemonitaceae 



A. Fructification aethalioid; capillitium charged with vesicles 1. Brefeldia 



B. Sporangia distinct, or nearly so. 



a. Stipe and columella jet-black. 



1. Capillitium so united as to form a surface net 2. Stemonitis 



2. Capillitial branch-tips free ... 3. Comatricha 



b. Stipe and columella whitish; calcareous . . 4. D'tachaea 



1. Brefeldia Rostafinski 



1873. Brefeldia Rost., Versuch, p. 8. 



Sporangia occupying in the asthalium several layers, those of the 

 median, and especially of the lowest layers, furnished with columellas 

 which blend beneath ; capillitium threads in the lowest layers arising 

 from the columella, in the upper extending radiately between the 

 individual sporangia, and united at the sporangial limits by means of 

 rather large inflated sacs. 



The genus Brefeldia is, like some others, difficult to dispose of in 

 any scheme of classification where linear sequence must be followed. 

 Rostafinski placed it in an order by itself. Its relationships are on 

 the one hand with Arnaurochaete and Reticularia, and on the other 

 with the Stemonitales, though easily distinguished from either. It is 

 intermediate to Arnaurochaete and StemonitiSj and withal, as it ap- 

 pears to us, a little nearer the latter, as the limits of the individual 

 sporangia are in Brefeldia pretty well defined. 



1. Brefeldia maxima (Fr.) Rost. 



Plate V., Figs. 7, 7 a, 7 b, and Plates XXL, XXII. 



1825. Reticularia maxima Fries, Syst. Orb. Veg., I., p. 147. 

 1875. Brefeldia maxima (Fr.) Rost., Versuch., p. 8. 



/Ethalium large, four to twenty cm, papillate above, violet-black at 

 first, then purple or purple-brown, developed upon a widespread, 



