PAPER. 



[ .577 j 



PARAaiTES. 



must be takeu on this accouut to avoid 

 errors from the accidental presence of them 

 ■\vlien blotting- -paper is used to absorb these 

 reagents when applied to objects on a slide. 

 The determination of the nature of the tila- 

 ments of which a paper is composed, by tlie 

 aid of the microscope, requires a thorough 

 knowledge of the characters of vegetable 

 fibres. The structure of the various fibres 

 is noticed under the individual heads. Lat- 

 terly the use of the fibres of the purple bog 

 melic-grass, Molinea ccerulea, has been in- 

 troduced. 



Rice-paper, as it is termed, is a totally 

 different material, consisting of thin layers, 

 cut by a peculiar operation, of the pith of 

 Aralia papyrifera, a Chinese Araliaceous 

 tree : this consists of parenchymatous cel- 

 lular tissue. 



Papyrus, consisting of pressed superposed 

 lamina? of the pith of the Papyrus plant, 

 Papyrus antiquorum, a kind of Sedge, ex- 

 hibits the lax parenchymatous structure 

 chaiacteristic of similar tissues, as in the 

 Rushes, &c. 



PAPER, METEORIC, and Aeeophytes. — 

 The structure of these substances is the 

 same as that of the so-called natural Hanuel 

 (Flanistel). They were formerly regarded 

 as of meteoric origin. They have been ob- 

 served in some in.^tances to fall from the 

 air, having been wafted perhaps many miles 

 from their place of formation by whirlwinds 

 and hurricanes. 



BrBL. Ehr. Abhandl. d. Berl. Akad. 

 1838. 



PAP'PUS.— The free portion of the 

 calyx of the Compositse. It may be 

 featherv, spiny, membranous, or hairy. 



PAPULASTORA, Preuss.— A genus of 

 Mucedines (Hyphoniycetous FuugiJ, con- 

 sisting of a decumbent articulate mycelium 

 sending up erect pedicels bearing a cellular 

 head, each cell supporting an oblong spore. 



P. sepedonioides has been found on rice- 

 paste. 



BiBL. Berk, and Broome, Ann. N. H. 2. 

 xiii. 4G2 ; Berk. Crijpf. Bot. 305, fig. 69 b. 



PAPY'RUS.— The pith of the stem of * 

 the Papyrus antiquormii (modern papyrus 

 from P. syrtacus), cut into slices, which are 

 laid upon one another and pressed so as to 

 form a compact stratum. Sections display 

 the parenchymatous tissue more or less de- 

 formed bv pressure. 



PAPACY 'PRIS, Sars. — A genus of 

 Cypridce (Entomostraca), near Ayluia and 

 Potamocyyris. One British species, rather 



common, marine ; also fossil in raised 

 beaches, &c. (Brady, Zm«. 2/-. xxvi. 377.) 

 PARADUXOS'TUMA, Fischer.— A ge- 

 nus of Cytheridce (Entomostraca). Valves 

 thin, smooth, elongate, compressed, sub- 

 ovate or subtiiangular ; mouth simple, tubi- 

 fbrm ; five joints in the lower, six in the 

 upper antennte, the last very slender. 

 Marine ; 13 British species. P. variahile 

 very common, fossil in raised beaches, &c. 

 (Brady, Linn. Tr. xxvi. 456.) 



PARAME'CIUM, Hill, Ehr.— A genus 

 of Holotrichous Infusoria, family Colpodina. 

 Char. Body compressed, covered with 

 cilia ; no eye-spot ; moutii lateral and with- 

 out projecting cirri. 



Several species, freshwater and marine. 

 P. aurdia (PL 31. figs. 56 and 57). Body 

 cylindrical, ovate-oblong, rounded or obtuse 

 at the ends, with an oblique longitudinal 

 fold extending to the mouth. Length 1-120 

 to 1-100" ; in vegetable infusions. 



This common infusorium shows well the 

 curious star-shaped contractile vesicles. 

 Ehrenberg notices in it the periodical occur- 

 rence of small black crystalline particles at 

 the anterior end. The depressions on the 

 surface of the integument (PI. 32. tig. 1) are 

 distinctly seen in the dried animal ; tri- 

 chocysts are present. 



P. chrysalis, E. (^Pleuronem'i crassum, D, 

 PI. 32. fig. 37, undergoing division). Body 

 oblong, cylindrical; oral cilia very long. 

 Length 1-2-10". 



BiBL. Elir. Inf. 349; Duj. Inf. 481; 

 Stein, Infus. ; C laparede et Lachmann, Infus. 

 265 ; Kent, Inf. 483. 



PARAISJ 'UNAS, Kt.— A genus of Fla- 

 gellate Infusoria. Free, ovate or globular, 

 one tiagellum, a distinct mouth at its base- 

 Four species, white, red, or green ; fresh- 

 water. (Kent, Inf. 370.) 



PARAPHY'SES.— The name apphed 

 to more or less delicate-jointed, hair-like 

 filaments Avhich occur in small numbers 

 around and between the antheridia and 

 archegonia of Mosses and Hepaticse (fig. 23, 

 p. 57, fig. 327, p. 388). The same term is 

 applied to simple tubular, more or less 

 clavate cells, occurring in large numbers 

 among the spore-sacs (asci and thecce) of 

 the Ascomycetous Fungi and the Lichens 

 (fig. 40, p. "78; fig. 398, p. 463; PL 37. 

 figs. 6, 12). 



PARAPONTEL'LA, Br.— A genus of 



Copepodous Entomofttraca. P. brevicornis, 



marine. (Brady, Copepoda, Hay Soc. i. 68.) 



PARASITES. — Under this head are in- 



2p 



