104 THE MYXOMYCETES 



whole covered by a white, foam-like crust composed of stellate lime 

 crystals; inner peridium delicate; capillitium of slender, limeless 

 threads, more or less branched, terminating in the walls of the tubes 

 and marked with occasional swellings or thickenings. 



By the descriptions offered by most authors, and especially by 

 Rostafinski's figures (Mon., pi. 9, fig. 158), a pronounced columella is 

 called for in the structure of Spumaria. The individual tubes rise 

 from a common hypothallus, and occasionally portions of this run up 

 and give the appearance of stipitate sporangia. Sometimes also this 

 upper extension of the hypothallus passes beyond or behind the base of 

 such a tube or between two or more, and is more or less embraced by 

 these in their confluent flexures. This, it seems, suggested Rostafinski's 

 elaborate diagram; at least, no other form of columella is shown by 

 American materials at hand. 



A single species: — 



Mucilago spongiosa (Leyss.) Morg. 



Bot. Gazette 24 : 56. 1897. 

 PI. VII, Figs. 149, 150. 



1783. Mucor spongiosus Leysser, Fl. Hal. 305. 



1791. Reticularia alba Bull., Champ. Fr. 92. 



1791. Spumaria mucilago Pers., in Gmel., Syst. Nat. 2 : 1466. 



1805. Spumaria alba (Bull.) DC, Fl. Fr. 2 : 261. 



1829. Didymium spumarioides Fr., Syst. Myc. 3 : 121, non Symb. Gast. 1818. 



1833. Diderma spumariccforme Wallr., Fl. Crypt. Germ. 2 : 374. 



^Ethalium white or cream colored, of variable size and shape, 1-7 cm. 

 in length and half as broad, the component tubes resting upon a 

 common hypothallus and protected by a more or less deciduous cal- 

 careous porous cortex; peridial walls thin, and where exposed, iri- 

 descent, generally whitened by a thin coating of lime crystals; cap- 

 illitium scanty, of simple, mostly dark colored, slightly anastomosing 

 threads; columella indefinite or none; hypothallus white, spongy; 

 spore-mass black; spores violaceous, exceedingly rough, large, 12-15 p. 

 Plasmodium creamy white. 



The plasmodium is dull white, of the consistency of cream, and is 

 often met with in quantity on beds of decaying leaves in the woods. 

 In fruiting, the plasmodium ascends preferably living stems of small 

 bushes, herbaceous plants, or grasses, and forms the aethalium around 

 the stem some distance above the ground. The cortex varies in amount, 

 is also deciduous, so that weathered or imperfectly developed forms 

 probably represent the form described as Spumaria cornuta Schum. 



Two varieties of this species are recognized; one from Bolivia, var. 



