124 THE NORTH AMERICAN SLIME-MOULDS 



The distinction between the two genera is almost an artificial 

 one, and species are sometimes arbitrarily assigned to one genus 

 or the other. The diagnosis in any case turns upon the pres- 

 ence or absence of a surface net, formed (in Stemonitis} by 

 the anastomosing of the ultimate divisions of the capillitial 

 branches. In ComatricJia the anastomosing is general, from 

 the columella out, and is not specialized at the surface. 



Recent attempts to reunite the genera here compared seem 

 to result in no apparent advantage. The genera come very 

 near together, but their separation along the line suggested by 

 Rostafinski remains convenient. 



Key to the Species of Comatricha. 



A. Sporangia closely crowded. 



a. Obovate, tufts small I. C. ccespitosa 



b. Elongate, ferruginous, tufts large . . . n. C.flaccida 



B. Sporangia various, generally scattered more or less widely. 



a. Capillitium very lax, the branching open. 



1. Sporangia much prolonged, 10- 1 2 mm. . . 2. C. longa 



2. Sporangia shorter, capillitium irregular . 3. C. irregularis 



3. Sporangium minute, ovate . . . 4. C. laxa 



b. Capillitium dense. 



1. Sporangia very small, 1-2 mm. 



i. Cylindric. 



* Nearly sessile . . 9. C. persoonii 



** Evidently stipitate . . 7. C. stemonitis 



ii. Spherical or ellipsoidal . . . . 5. C. nigra 



iii. Ovate acuminate . . . 6. C. pnlcJiella 



2. Sporangia larger. 



i. Black 10. C. suksdorfii 



ii. Pale ferruginous . . . . 8. C. equalis 



i. COMATRICHA CCESPITOSA Stnrgis. 



PLATE XI., Figs. 12, 13, 14. 

 1893. Comatricha ccespitosa Sturg., Bot. Gaz., XVIII., p. 186. 



Sporangia densely crowded or cespitose, sub-sessile or short 

 stipitate, clavate, 1-1.5 mm - high, the peridium gray iridescent 

 with blue tints, comparatively permanent but finally disappear- 

 ing ; columella attaining two-thirds to three-fourths the height 



