perichaena] arcyriaceae 249 



2. P. depressa Libert PI. Crypt. Ard., fasc. iv. no. 378 

 (1837). Plasmodium milky - white. Sporangia sessile, 

 crowded, polygonal from mutual pressure, flattened, 0-5 to 

 1 mm. diam., sometimes forming short branching plasmodio- 

 carps, purple- brown, red-brown, buff or grey, dehiscing along 

 the margin with a well-defined lid ; sporangium-wall of two 

 layers, the outer cartilaginous, charged with brown granular 

 matter, often intermixed with angular crystals of lime, more 

 or less closely combined with the membranous smooth inner 

 layer. Capillitium an abundant web of branched slender 

 yellow threads, 1-5 to 2-5 p diam.. minutely warted or marked 

 with regular close-set constrictions at intervals of 0-5 to 1 p, 

 and with irregular expansions. Spores golden-yellow, 

 minutely warted, 8 to 12 p diam. — Rost. Mon., p. 292 ; Mass. 

 Mon., 114 ; Macbr. N. Am. Slime-Moulds, 183. Stegasma 

 depressum Corda Icon., v. 58, t. hi., fig. 34 (1842). S. australe 

 Cesati in Hedw., xiii. 186 (1874). Perichaena artocreas Berk. & 

 Rav. in Grev., ii. 68 (1873). P. irregularis Berk. & Curt. 

 in Grev., ii. 68. P. marginata Berk. & Br. in Journ. Linn. 

 Soc, xv. 84 (1876) (non Schwein). P. australis Berl. in Sacc. 

 Syll., vii. 422 (1888) ; Mass. I.e., 119. P. applanata Mass. 

 I.e., 116 (1892). P. quadrata Macbr. I.e., 184 ? Hemiarcyrin. 

 applanata Cooke & Mass. in Grev., xvi. 20 (1887). Ophiotkeca 

 irregularis Mass. I.e., 132. 



PI. 1S9. — a. sporangia ; b. capillitium and spores with a fragment of the double 

 sporangium-wall ; c. capillitium and spore ; (England). 



This species is distinguished from P. corticalis, to which it is closely 

 allied, by the flattened sporangia and smaller spores. The type of 

 P. applanata Mass., from Brisbane (K. 153), is characterised by the 

 outer layer of the sporangium-wall having a superficial crust of angular 

 crystals of lime, which gives the sporangia a lilac-grey colour ; in all 

 other respects, in the abundant and minutely-warted capillitium, and 

 in the spores measuring 10 to 11 p diam., it agrees with the nresent 

 species ; deposits of lime on the sporangium-wall are of frequent 

 occurrence both in P. depressa and in P. corticalis, and although they 

 are unusually abundant in the Brisbane specimen, the character is not 

 of sufficient importance to give specific distinction. The type of 

 P. artocreas Berk. & Rav. from South Carolina (K. 1027 and B.M. 697) 

 appears also to be P. depressa ; it has abundant capillitium, and spores 

 measuring 8 to 10 p. ; the sporangia are polygonal, depressed, and 

 pale brown. The type of P. irregularis Berk. & Curt, from South 

 Carolina (K. 1706) is typical P. depressa. The type of Stegasma 

 australe Ces. from Naples (B.M. 1034) is in imperfect condition, but it 

 appears to be the present species from the many broken pieces of 

 minutely warted capillitium, and the spores, which measure 10 to 11 p. 

 diam. Stegasma pallida Ces. (in Atti Accad. Sc. Fis. Mat., viii. 12, 

 1879) from Borneo may possibly be a form of P. depressa, but the 

 description is too brief to be instructive. 



Perichaena Krupii Racib. (in Hedw., xxviii. 124 (1889) ) is described 

 as having solitary chestnut-brown globose depressed sporangia or 



