PLOCAMIUM. 



[ 609 ] 



PODISOMA. 



from the last ; posterior branch with three 

 setas, all arising from the last joint. 



P. uncinatus. Beak curved upwards at 

 the end ; 3 sharp spines at anterior inferior 

 ansrle of shell ; inferior antennae as the last. 

 P. hamatus. Beak blunt and strong, 

 slightly curved downwards; first pair of 

 legs with a curved claw at the end. ? Male 

 of P. trigonellus. 



BIBL. Baird, Brit. Entomostr. p. 134. 

 PLOCA'MIUM, Lamouroux. A genus 

 of Delesseriaceae (Florideous Algae), con- 

 taining one species, P. coccineum (PI. 4. 

 fig. 10), the commonest of our red sea- 

 weeds, with a delicate flat feathery thallus, 

 from 2 to 12" high, growing in bushy tufts 

 on rocks or other Algse. The fruit consists 

 of : 1. coccidia, spherical, stalked or sessile 

 tubercles, at the .sides or in the axils of the 

 ramules, filled with angular spores ; 2. an- 

 theridia, which occur in inconspicuous flat 

 patches, composed of short erect cells, upon 

 the surface of distinct plants ; and 3. sti- 

 chidia, lateral or axillary, simple or branched 

 pods containing a single or double row of 

 linear (transversely parted) tetraspores. 



BIBL. Harvey, Mar. Alg. 19; Phyc. 

 Brit. pi. 44; Grev. Alg. Brit. pi. 12; Thuret, 

 Ann. Sc. Nat. 4 ser. iii. 19. 



PLCEO'TIA, Duj. A genus of Infusoria, 

 family Thecamonadina. 



Char. Body diaphanous, with several 

 longitudinal ribs or keels in the middle, and 

 a rounded perfectly limpid margin. Two 

 anterior locomotive filaments, one flagelli- 

 form, the other trailing and capable of 

 arresting the movement of the body. 



P. vitrea (PI. 31. fig. 67). Marine; length 

 1-1200". Movement slow. 

 BIBL. Duj. Infus. 345. 

 PLCESCO'NIA, Vul., = Euplotes, Ehr. 

 PLUMATEL'LA, Lamk. A genus of 

 freshwater Polyzoa, order Hippocrepia, 

 family Plumatellidae. 



Char. Zoary confervoid, branched, tubu- 

 lar, branches distinct ; tentacular disk cre- 

 scentic ; ova elliptical, with a marginal ring, 

 but no spines. 



P. repens. Zoary irregularly branched ; 

 cells subclavate, without a longitudinal fur- 

 row or keel ; tentacles about 60 ; tentacular 

 membrane dentate ; ova broad. 

 a. Adherent throughout. 

 (3. Attached only at the base. 

 P. fruticosa. Irregularly branched, at- 

 tached at the origin only ; cells cylindrical, 

 and destitute of furrow, but obscurely 

 keeled ; ova elongated. 



P. corattoides. Attached at the base only ; 

 tubes dichotomous, densely tufted, desti- 

 tute of furrow and keel; tentacles about 

 60 ; ova broad. 



BIBL. Allman, Freshiv. Polyz. 92 ; Ann. 

 N. H. 1844, xiii. 330 ; Johnston, Br. Zooph. 

 402; Parfitt, Ann. N. H. 1866, xviii. 171. 



PLUMULA'RIA, Lanik. A genus of 

 Hydroid Zoophytes, family Plumulaiiidae. 



Char. Polypidom plant-like, rooted, sim- 

 ple, or branched, feathery ; cells small, uni- 

 lateral, usually seated in the axilla of a 

 horny spine; egg-vesicles scattered. Ten 

 British species. 



P. cristata. Stem simple, a single tube, 

 pinnate; pinnae alternate; cells close, rim 

 toothed ; vesicles gibbous, girt with crested 

 ribs. 



P. falcata. Stem a single tube, waved, 

 branched, branches alternately pinnate ; 

 cells close, shortly tubular, rim entire ; egg- 

 vesicles oval-oblong; common. 



In P. myriophyttum & P. frutescens, the 

 stem consists of several parallel tubes. 



P. pinnata. Linn. Stem a simple tube, 

 plumose; pinnae alternate, three on each 

 internode ; cells rather distant, campanulate, 

 appressed, rim entire ; vesicles pear-shaped, 

 rini toothed. 



P. setacea, Ellis. Stem a single tube, 

 pinnate ; pinnae alternate, one at each joint ; 

 joints ringed ; cells very remote, campanu- 

 late, rim even ; vesicles elliptical, smooth ; 

 common. 



BIBL. Johnston, Br. Zooph. 89 ; Hincks, 

 Hyd. Zooph. i. 294. 



'PLUMULARI'nm A family of Hy- 

 droida. 



BIBL. Hincks, Hyd. Zooph. i. 279. 



PODAXINE'L A family of Gastero- 

 mycetous Fungi, none of which are found 

 in Britain ; they are distinguished from all 

 allied tribes by a solid column in the centre 

 of the sporange. 



Many of the species grow on the hills of 

 the White Ant. 



BIBL. Montagne, Ann. Sc. Nat. 2. xx. 

 69; Tulasne, Ann. Sc. Nat. 3. iv. 169; 

 Currey, Linn. Tr. xxvi. 288. 



PODISO'MA, Link. A genus of Uredi- 

 nei (Hypodermous Fungi), growing upon 

 the living leaves and branches of species of 

 Juniper; the filamentous mycelium creeping 

 beneath the epidermis, and sending up a 

 fleshy, stalk-like, tremelloid body (fig. 589), 

 composed of agglutinated filaments (fig. 590) 

 terminating in bilocular spores (or two 

 spores adherent together), each of the cells 



