The .'\ryxoiiiyi'("tes of (he Miami I'a/Zey, Ohio. 129 



often, being elongated and flexuous, the}' branch and anasto- 

 mose freely, their walls Ijeconiing perforated and more or less 

 defective ; in other cases, the cethalinm is a compound plas- 

 modiocarp, the narrow sinuous sporangia branched and 

 anastomosing in all directions, forming an intricate network, 

 closely packed together and inseparable. The surface of the 

 aethalium is often covered by a continuous layer of some 

 excreted substance, which is called the common cortex. 



The wall of the sporangium, typically, is a thin, firm mem- 

 brane, colorless and pellucid, or colored in various shades of 

 violet, brown, yellow, etc.; it is sometimes extremely delicate, 

 as in Lamproderma, or is scarcely evident, as in Stemonitis; 

 in other instances it is thickened by deposits on the inner 

 surface, as in Tubulina, or by incrustations on the outer sur- 

 face, as in Chondrioderma. The stipes are tubes usually with 

 a thick wall, which is often wrinkled and folded lengthwise, 

 and is confluent above with the wall of the sporangium ; in 

 some cases the stipe also enters the sporangium, and is more 

 or less prolonged within it as a cohonella. The stipe com- 

 monly expands at the base into a membrane, which fastens 

 it to the substratum, and is called the hypothallus ; when all 

 the stipes of the same group of sporangia stand upon a single 

 continuous membrane, it is called a commo)i hypotJialhis. 



In the simplest forms, the cavity of the sporangium is filled 

 exclusively with the numerous spores ; but in most all of the 

 genera, tubules or threads of different forms occur among 

 the spores and constitute the capillitium. The capillitium 

 first makes its appearance in Reticularia, in which upon the 

 inner surface of the walls of the sporangia there are abundant 

 fibrous thickenings ; next in Cribraria it is spread over the 

 inner surface of the wall, and is early separated from it; here, 

 also, it first assumes a more definite form and arrangement ; 

 in Physarum it is in connection with the wall of the sporan- 

 gium only b}^ its extremities while it traverses the interior 

 with a complicated network ; in Stemonitis and its allies the 

 capillitium originates wholly from the columella ; in most 

 species of Arcyria it issues from the interior of the stipe. 

 The capillitium in Trichia consists of numerous slender 

 threads which aire free, that is, are not attached in any way; 

 they are usually simple and pointed at each extremity : the 

 surface of these threads exhibits beautiful spiral markings. 



