DiDYMIUM 131 



thick, white, smooth or scaly, or glossy brownish purple when 

 without lime; sporangial wall dehiscing irregularly, membranous 

 or somewhat stouter, colorless, mottled with yellow or pale pur- 

 plish, with a crust of minute, stellate, rod-shaped, or nodular 

 crystals of lime; crust often broken into numerous discoid or 

 concave scales, 0.1 to 0.2 mm. diam., each scale attached by the 

 center to the membranous layer. Columella convex or repre- 

 sented by the colorless or yellowish brown base of the sporangial 

 wall, which is usually thickened beneath with a network of 

 strands containing a few minute lime-crystals. Capillitium abun- 

 dant, of pale brownish purple threads, often slender, more or less 

 connected by transverse bars, and combined to form an elastic 

 network, readily separating from the sporangial wall. Spores 

 purple-brown, minutely or strongly and closely spinulose, 9-17 /x 

 diam. 



Type locality: Europe. 



Habitat: On herbaceous stalks and twigs. 



Distribution: *CoIorado. 



Illustration: Lister, Mycetozoa ed. 3. pi. 194, as D. 

 Wilczekii. 



This species is distinguished from D. Listen, which also has 

 transverse, connecting bars between the threads of the capilli- 

 tium, by the more pulvinate plasmodiocarps, the elastic capil- 

 litium separating as a mass, the usually larger spores, and other 

 minor characters. Transverse, connecting bars are found occa- 

 sionally in other forms of Didymium, but those species can be 

 recognized by other characters. D. nivicolum Meylan is a phase 

 of the present species with a scaly sporangial wall like that seen 

 often in D. squamulosum. 



18. Didymium crustaceum Fries, Syst. Myc. 3: 124. 1829. 



Plasmodium white (Lister). Sporangia confluent, clustered, 

 or scattered, short-stalked or sessile, globose, 0.7 to 2 mm. diam., 

 smooth and white from the thick, fragile, deciduous crust of 

 loosely compacted crystals of lime in which they are enclosed; 

 when the crust has fallen away the sporangia appear reniform 

 or hemispherical and gray; sporangial wall membranous, color- 

 less, clothed with large stellate crystals of lime. Stalks pale bufl", 

 0.2 to 0.4 mm. high, slender, membranous, several often clustered 

 together on an expansion of the membranous hypothallus, at first 



