ARCYRTA.] ARCYRIACEjE. 187 



This species is very variable in the shape of the sporangia. An 

 extensive growth of the common grey form, arising from one develop- 

 ment of plasmodium, will often exhibit much diversity ; subglobose 

 sporangia with short stalks and subcylindrical sporangia with long 

 stalks are found in company with the more usual ovoid form, either 

 single, or combined in clusters of two to five, and then correspond with 

 A. digitata Rost. Groups are also met with on dead bramble stems in 

 which the nearly white sporangia are shortly stalked and perfectly 

 globose, 0'5 to 0'7 mm. diam. ; but these are associated with other 

 groups, showing all degrees of difference from subglobose to ovoid. 

 Specimens from North and South America and from the tropics are 

 usually elongated or cylindrical. The marking on the capillitium is 

 also a variable character. In some gatherings of the grey form the 

 threads are nearly uniform throughout, and either almost smooth, or 

 spinulose, with the spines minute and equally distributed, or 1 to 2 /z 

 long, either sharp-pointed or thickened at the apices ; in other gather- 

 ings the threads are broad and papillose, as in Lachnobolus circinans. 

 A. pom if or mis Roth, has yellow globose sporangia and slender stalks, 

 but the capillitium in the type specimens in Strassburg Herbarium 

 does not differ, except in colour, from that frequently met with in the 

 grey form. A. globosa Schwein. (Lachnobolus globosus Rost.) appears 

 to be a variety of A. albida occurring on the burs and catkins of 

 chestnut in the United States : the globose sporangia measure O3 to 

 O5 mm. diam., and are nearly white or pale ochraceous ; the stalks are 

 slender, one to one and a half times the length of the sporangium ; the 

 capillitium and spores resemble those of A. albida in all respects. 

 Specimens received from Dr. Rex represent two varieties : one is con- 

 fined to the burs of chestnut ; the other, named var. minor by Ellis, is 

 smaller, with longer stalks, and grows exclusively on the catkins. 

 These forms on chestnut seem to be constant in shape ; in English 

 gatherings, however, the form growing on bramble stems has usually a 

 marked character, differing from those found on stumps in the more 

 globose and smaller sporangia with short stalks, and though these 

 characters are less constant than those of the American gatherings, it 

 would appear that the latter may owe their shape to the special substances 

 on which they grow, and are not specifically distinct from A. albida. 

 The type specimen of A. Friesii Berk. & Br. (K. 896) is the grey ovoid 

 form of A. albida, with typical capillitium and spores. A. digitata 

 Rost. is the cylindrical form of A. albida, with sporangia mostly in 

 clusters of three to seven together ; the stalks usually equal the 

 sporangia in length, and, though adhering, are easily separable ; the 

 " botrytis " arrangement cannot be viewed as having any specific value. 

 The type of A. Cookei Mass., from Brazil (Trail K. 865), is a tall grey 

 form of A. albida ; the sporangia measure 2 mm. in length, O5 mm. in 

 breadth ; the stalks are 2 mm. long, Ol mm. thick ; the capillitium and 

 spores are quite typical. 



Hub. On dead wood, etc. a. Batheaston, Somerset (B. M. 276, 281) ; 

 /3. Batheaston (B. M. 278) ; a. Lyme Regis, Dorset (L:B.M.155) ; a. Sib- 

 bertof t, Norths. (K. 896) ; a. France (K. 859) ; a. Germany (B. M. 713) ; 

 a. and ]3. Poland (Strassb. Herb.) ; a. Cape (K. 858) ; a. Japan (K. 866) ; 

 a. Borneo (L:B.M.155) : a. Australia (B. M. 714) ; Tonga Tabu 

 (L:B.M.155) ; /3. New Jersey (K. 877) ; a. Iowa (B. M. 828) ; y. Phila- 

 delphia (L:B.M.155) ; y. Ohio (K. 882) ; a. S. Carolina (B. M. 972, 976) ; 

 a. Cuba (B. M. 716) ; a. Nicaragua (B. M. 1030) ; a. Venezuela 

 (B. M. 715) ; a. French Guiana (Paris Herb.) ; a. Brazil (K. 865). 



