86 THE NORTH AMERICAN SLIME-MOULDS 



resting on a thin venulose hypothallus, or sometimes globose, 

 the peridium dark colored, with a thin layer of stellate crystals, 

 irregularly ruptured ; capillitium of slender, dark-colored threads, 

 which extend from base to wall, more or less branched, and 

 combined into a loose net ; columella a thin layer of brown 

 scales ; spores globose, very minutely warted, violaceous, 8-9 yu.. 

 This minute species is reported, so far, from Ohio only. It 

 resembles a poorly developed, or sessile, phase of D. niclano- 

 spennnm. Some of the sporangia (?) are spherical, and certainly 

 show a short brown stalk. The columella is scant, and the 

 spores are smaller than those of D. mclanospermum. 



3. DIDYMIUM CRUSTACEUM Fries. 



1829. Didymium crustaceum Fries, Syst. Myc., III., p. 124. 



Sporangia closely aggregated, globose, or by compression de- 

 formed, sessile, snow white, by virtue of the remarkably devel- 

 oped crust of calcareous crystals by which each sporangium is 

 surrounded as in Diderma ; the peridium membranous, color- 

 less, frosted with large stellate crystals, usually shrunken above 

 and depressed ; columella pale, small, or obsolete ; hypothallus 

 scant or not continuous ; capillitium of rather stout violaceous 

 threads seldom branched except at the tips, where they are 

 pale and often bifid, or more than once dichotomously divided ; 

 spores strongly warted, globose, violet brown, 10-13 A 1 - 



This species has all the outward seeming of a Diderma, but 

 cannot be referred to that genus because of the crystalline 

 character of its crust. This is a very marked structure, loosely 

 built up of very large crystals ; it is necessarily extremely frail, 

 nevertheless persists arching over at a considerable distance 

 above the peridium proper. 



The sporangia are said to be sometimes stipitate. This fea- 

 ture does not appear in any of the material before me. Lister 

 in Mycetozoa PI. XL., c. draws the capillitium much more deli- 

 cate than it appears in our specimens. The hypothallus is 

 sometimes noticeable under some of the sporangia where 

 closely crowded, but is not a constant feature. 



