196 ENDOSPORE,. [PERICTTJENA. 



KEY TO THE SPECIES OF PERICH^ENA. 



A. Sporangium-wall stout, brown, black or grey, inner layer 



smooth. 



Capillitium spinose, abundant. 1. P. chrysosperma 



Capillitium minutely warted, abundant; spores 10 to 

 11 ft diam. 2. P. depressa 



Capillitium minutely warted or nearly smooth, 

 scanty; spores 12 to 14 ft diam. 3. P. popuUna 



B. Sporangium-wall yellow or pale umber, inner layer papillose. 



4. P. variabilis 



1. P. chrysosperma Lister. Plasmodium pale brown, in rotten 

 bark. Sporangia subglobose, sessile, or shortly stalked, often 

 forming horse-shoe or ring-shaped plasmodiocarps, scattered, 

 0'4 to 1 mm. diam,, chestnut or red-brown, dehiscing irregularly; 

 sporangium-wall of two layers, the outer composed of brown 

 granular matter, which either forms a complete crust, or is more 

 or less obsolete ; the inner layer subcartilaginous, yellowish-olive, 

 translucent. Stalk, when present, stout, black. Capillitium 

 abundant, forming a loose network of sparingly branched yellow 

 threads 2 to 4 ft diam., irregularly constricted, spinose, spines 

 1 to 6 ft long, subulate, curved, scattered. Spores citron-yellow 

 in mass, minutely warted, 9 to 10 ft diam., rarely 7 to 8 ft. 

 Ophiotheca chrysosperma Currey, in Quart. Micr. Journ.,ii., p. 240 

 (1854). Trichia circumscissa Wsillr., Fl. Cryp. Ger., p. 378 (1833). 

 Cornuvia circumscissa Host., Mon., p. 290 ; Cooke, Myx. Brit., 

 p. 76. Ophiotheca circumscissa Mass., Mon., p. 131. Ophiotheca 

 Wrightii Berk. & Curt., in Journ Linn. Soc., x., p. 349 ; Mass., 

 Mon., p. 132. Cornuvia Wrightii Host., Mon., App., p. 36; 

 Macbride, in Bull. Nat. Hist. Iowa, ii., p. 122. 



Plate LXXL, A. a. sporangia, stalked and sessile, x 20 ; &. Capillitium 

 from different sporangia growing on the same piece of walnut bark, and 

 spore, x 600 (England). 



It would appear that Rostafinski excluded this species, which he 

 named Cornuvia circumscissa, from the genus PericJuvna, because he 

 defined that genus as having capillitium without characteristic 

 thickenings ; but in P. populina, to which this definition most nearly 

 applies, the capillitium is usually closely warted and notched, rarely 

 smooth, while in some gatherings the threads are beset with scattered 

 sharp spines in addition to crowded spinules. In P. depressa and 

 P. vermicularis the capillitium is never smooth, though the thickenings 

 may be reduced to minute warts ; the character given by Rostafinski 

 is therefore inapplicable, and in every feature except the large 

 development of spines on the threads, P. chrysosperma is closely allied 

 to the other members of the group. In a gathering of this species at 

 Lyme Regis, two of the sporangia examined have smooth threads with 

 a few minute spines distantly scattered, in others the spines are of the 

 usual form, loosely set, and about 2'5 p. long ; but in the greater number 

 of sporangia the spines measure 5 to 6 '5 p in length. The characters 



