6 THE NORTH AMERICAN SLIME-MOULDS 



ture is recognizable, either directly, when the sporangium is 

 sessile, or by the intervention of a stipe. The stipe may be 

 hollow, may contain coloring matter of some sort, or may even 

 contain peculiar spore-like cells or spores ; is often furrowed, 

 and in some cases shows a disposition to unite or blend with 

 the stalks of neighboring sporangia. In many cases the stipe 

 is continued upward, more or less definitely into the cavity of 

 the sporangium, and there forms the columella, sometimes 

 simple and rounded like the analogous structure in Mucor 

 mnccdo, sometimes as in Comatricha, branching again and again 

 in wonderful richness and complexity. 



Each sporangium is at maturity filled with numerous unicellu- 

 lar spores. These are usually spherical, sometimes flattened at 

 various points by mutual contact; they are of various colors, 

 more commonly yellow or violet brown, are sometimes 

 smooth (?), but generally roughened either by the presence 

 of minute warts, or spines, or by the occurrence of more or 

 less strongly elevated bands dividing reticulately the entire 

 surface. The spores are in all cases small (0.003-0.020 mm.) 

 and reveal their surface characters only under the most excel- 

 lent lenses. Associated with the spores in the sporangium 

 occurs the capillitium. This consists of most delicate thread- 

 or hair-like elements, offering the greatest variety both in form 

 and structure. The threads composing the capillitium are not 

 to be regarded, even when free, as cells, nor even of cellular 

 origin ; they are on the other hand, in such a case, simply 

 shreds and strands of the original plasmodium, portions that 

 have not been used in the formation of spores, and are accord- 

 ingly modified in such wise as to be useful in spore-dispersal. 

 The capillitium threads may be solid or hollow, they may 

 occur singly or be combined into a net, they may be terete or 

 flat, attached to the peridial wall or free, simple or adorned 

 with bands or spires and knobs in every variety, uniform or 

 profusely knotted and thickened at intervals, and burdened 

 with calcic crystals. In many cases, as remarked, the 

 capillitium contributes materially to the dispersal of the spores ; 



