didymium] didymiaceae 135 



hardly developed, represented by the colourless or yellowish- 

 brown base of the sporangium-wall, which is usually thickened 

 beneath with a network of strands containing a few minute 

 lime crystals. Capillitium very abundant, consisting of pale 

 brownish-purple often slender threads combined to form an 

 elastic network, readily separating from the sporangium- walls. 

 Spores purple-brown, minutely and closely spinulose, 9 to 

 13 fx diam. 



PI. 194. — a. b. plasmodiocarps (Jura Mountains) ; c. capillitium with fragments 

 of sporangium-walls ; d. spore. 



This alpine species resembles the stouter plasmodiocarp forms of D. 

 8quamulosum, from which it is distinguished by the absence of a prom- 

 inent columella, the dense elastic network of capillitium and the darker 

 spores. M. Ch. Meylan describes the repeated occurrence of D. Wilczekii, 

 often in great abundance, on open ground in the Jura Mountains at an 

 altitude of 1,100 to 1,300 m. It appears in sprmg-time only, directly 

 after the winter snows have melted ; the sporangia are very fugacious, 

 and a shower of rain is sufficient to wash them away. Dr. R. E. Fries 

 has gathered what appears to be a form of the present species in 

 subalpine situations near Frostviken, Jamtland, Sweden ; the long 

 stout plasmodiocarps either have lime deposits in the form of minute 

 rod-shaped crystals, or are entirely without lime ; the capillitium 

 threads are stout and dark ; the whole growth so closely resembles 

 the sporangia of Lepidoderma Carestianum often found associated with 

 it on the same twigs and herbage, that in writing to Dr. Fries we gave it 

 as our opinion that his specimens might be a " Didymium form " of 

 the latter species (seeR. E. Fries in Ark. Bot., vi. No. 7, p. 3, & Lister 

 in Journ. Bot., xlvi. 218). M. Meylan's observations, however, have 

 established the constancy of this alpine Didymium, and the Swedish 

 gatherings should be referred to D. Wilczekii. 



Hab. On turf and twigs in alpine situations. — Ste. Croix, Jura 

 (B.M. 2508) ; Arolla, Vallais, Switzerland (B.M. 2.309) ; Frostviken, 

 Sweden (B.M. 2.510). 



12. D. intermedium Schroet. in Hedwigia, xxxv. 209 

 (1896). Plasmodium ? Sporangia gregarious or clustered, 

 stalked, discoid, convex above, widely and deeply umbilicate 

 beneath, often lobed or sinuous, 0-5 to 1 mm. diam., greyish 

 white ; sporangium- wall membranous, clothed with super- 

 ficial deposits of lime crystals. Stalk 0-7 to 1 mm. long, pale 

 yellow or buff, broad at the base and tapering upwards, rilled 

 like the columella with crystalline nodules of lime. Columella 

 convex, discoid, pale yellow or white, formed by a shallow 

 thickening of the base of the sporangium-wall, recurved at the 

 margin owing to the deeply umbilicate character of the spor- 

 angium. Capillitium of simple or branched slender colourless 

 threads. Spores dark purple-brown, 9 to 12 /x diam., marked 

 with a close irregular reticulation of minute ridges making 

 a border about 0*7 \x deep. — D. excelsum Jahn in Ber. Deutsch. 

 Bot. Gesell., xx. 275, t. xiii, figs. 5 to 10 (1902). 



PI. 110. — d. sporangia, two have the walls and capillitium broken away exposing 

 the columella ; e. capillitium and spores ; /. spore ; (Brazil). 



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