POLYTIIALAMIA. 



[ 624 ] 



POLYTRICIIUM. 



sutures or over them. Orifices numerous, 

 arranged along the margin of, or forming a 

 triangle at, the upper part of the last cham- 

 ber. Polystomella passes into Naniojilna, 

 through P. striato-punctata (PL 24. f. 19), 

 common in cold seas. 



P. crispa (PI. 24. fig. 20) is common in 

 temperate seas. P. eraticulata is of tropical 

 growth. P. macdla (^Faujasina) is unsym- 

 metrical and starved. Many fossil forms. 



BiBL. D'Orbigny, For. Vien. 121 ; Wil- 

 liamson, Fornm. 39 ; Morris, Br. Fossils, 40; 

 Parker & Jones, Ann. X. H. 3. v. 103 ; 

 Carpenter, For. 276. 



POLYTHALA'MIA. See Fokamini- 



FERA. 



POLYT'OMA, Ehr.— A genus of Fla- 

 gellate Infusoria, family Mouadina (Hydro- 

 morina). 



P. iwella (PL 31. fig. 69, undergoing di- 

 vision), the only species, is oblong or oval, 

 obtuse at the ends, colourless, furnished with 

 two flagelliform filaments ; it has no cara- 

 pace. Fresh or decomposing water ; length 

 1-2200 to 1-960" ; size of body when the 

 division is nearly complete, 1-400". 



As it increases in size it assumes a wrinkled 

 or mulberry appearance, and this indicates 

 the approaching division into many sections, 

 whence the name. 



PiBL. Ehr. Inf. 24 ; Schneider, Ann. N. 

 II. 18o4, xiv. 321 ; Pritchard, Inf. 136 & 

 504 ; Kent, Inf. 301. 



POLYTRE'MA, Blainville.— A protean 

 parasitic Foraminifer of the Rotaline family ; 

 scale-like, globular, or arborescent, with 

 cancellated structure. P. miniucemn is 

 widely distributed in the Mediterranean and 

 other warm seas. 



BiBL. Carpenter, For. 235; Schultze, 

 TViepn. Arch. 1863, 81 ; Ann. N. H. 3. xii. 

 409 ;' Carter, ihid. 4. xvii. 185 ; 5. v. 440. 



POLYTRICIIA'CEyE. — A tribe of 

 MnioidciB (operculate Mosses of usually 

 Acrocarpous habit). 



Getiera. 



Cathnrwen. Calyptra narrowly hood- 

 shaped, subscabrous at the apex, rather hairy 

 within. Peristome simple, composed of 

 thiity-two teeth, arising from a narrow, 

 cellular basilar membrane, ligulate, mem- 

 branous, white, with many percurrent, 

 reddish, inarticulate iilaments, somewhat 

 incurved, scarcely hygroscopic, firm. Colu- 

 mella dilated at the apex into a drum-like 

 epiphragm. Capsule equal. InHorescence 

 monoecious or dioecious. 



Fig. 599. 



Pohjtrichinn. Calyptra dimidiate, but 

 appearing campauulate on account of a 

 quantity of very close hairs descending from 

 it as a long villous coat ; otherwise resem- 

 bling the preceding genus. 



POLYT'RICHUM, Dill.— A genus of 

 Poly trichaceous Mosses, variously defined by 

 diflerent authors. In the British'Flora, it in- 

 cludes the forms separated in this work under 

 Cathabinea, which in the 'Bryologia Bri- 

 tannica ' are divided between Atrichum and 

 OUyotrichum. The species of Pohjtriclnoa 

 comprised in our definition are distributed in 

 the same work under Poyonatum. (those with 

 a ronnd capsule and thirty-two teeth) and 

 Pohjtrichum proper (those with a square or 

 prLsmatic apophysate capsule (tig. 600 ), and 

 usually twice as many 

 teeth ). P. commune is 

 one of o ur finest Mosses, 

 common on heaths, 

 moors, and mountain 

 tracks, varying some- 

 what under the differ- 

 ent physical conditions. 

 The stems are from 

 6" to 1' long, and the 

 fruit-stalks 2 or 3". 

 The stems are almost 

 of woody texture, the 

 leaves large and firm. 

 The calyptra is den.sely 

 covered with hairs. 

 Wilson remarks that 

 the true structure of the 

 sporauge and columella 

 of Mosses may be most 

 easily learned from 

 the study of this 

 genus. The columella 

 is seen (figs. 601, 603), 

 to be separated from 

 the spores by an 

 imier layer of the spo- 

 rangial membrane. The 

 diaphragm attached 

 to the apices of the 

 teeth of the peristome is 

 the dilated apex of the columella (fig. 603). 



The peristome (fig. 602) is composed of 

 ligulate obtuse teeth, connected by a m(>m- 

 brane at the base, continuous with the inner 

 layer of the wall of the capsule. These 

 plants are also exceedingly Avell adapted for 

 the examination of the male inficn-escence 

 and spermatozcids. They are all dicecious ; 

 and the male plants (lig. 604) are readily 

 distinguishable by the cup-shaped infiores- 



Polytrichiim commune. 



Plants in fruit. 

 One half natural size. 



