PLOCAMIUM. 



[ 513 ] 



PODODISCUS. 



with a curved claw at the end. ? Male of 

 of P. trigonellus. 



BiBL. Bau-d, Brit. Entomostr. p. 134. 

 PLOCAMIUM, Lamouroux.— A genus 

 of Delesseriacese (Florideous Algse), contain- 

 ing one species, P. coccineum, the common- 

 est of our red sea- weeds, with delicate flat 

 feathery thallus, from 2 to 12" high, growing 

 in bushy tufts on rocks or other Algae. 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. antheridia, which occur 

 in inconspicuous flat patches, composed of 

 short erect cells, upon the surface of distinct 

 plants; and 3. stichidia, lateral or axillary, 

 simple or branched pods containing a single 

 or double row of linear (transversely parted) 

 tetraspores. 



BiBL. Harvey, Br. Mar. Alg. p. 19. 

 pi. 15 C; Phyc. Brit. pi. 44; Greville, Alg. 

 Brit. pi. 12; Thuret, Ann. des Sc. nat. 

 4 ser. ui. p. 19. 



PL(E6flA,'Duj.— A genus of Infusoria, 

 belonging to the family Thecamonadina. 



Char. Body diaphanous, with several 

 longitudinal ribs or keels projecting in the 

 middle, and a rounded perfectly limpid 

 margin. Two anterior locomotive filaments, 

 one flagelliform, the other trailing. 



P. vitrea (PI. 24. fig. 67). Body hyaline, 



with three orfour projecting longitudinal lines 



in the middle, and some internal granules. 



Marine ; length 1-1200". Movement slow. 



BiBL. Dujardin, Infus. p. 345. 



PLCESCONIA, Duj. (Infusoria) = Eu- 



plotes, Ehr. 



PLCESCONINA, Duj. (Infusoria).— 

 This family consists of the family ^Mj9Zo^a,E., 

 united with the genus Loxodes, E. 

 BiBL. Dujardin, Infus. p. 428. 

 PLUMATELLA, Lam. — A genus of 

 Polypi, of the order Bryozoa. 



Char. Polypidom fixed, coriaceous or 

 membranous, confervoid, tubular, branched; 

 polypes issuing from the ends of the 

 branches ; tentacular disc crescentic ; ten- 

 tacles numerous (about sixty), in a single 

 row, invested at then origin by a membrane. 

 Aquatic. Doubtfully distinct from Alcy- 

 onella. 



P. repens. Polypidom adherent, the erect 

 branches tubular, margins of apertm'es en- 

 tire. Stem several inches long. 



P. emarginata. Apertures with a deep 

 notch filled up by a transparent membrane. 

 P.fruticosa. Branches suddenly dilated 

 towards the entire apertures. 



BiBL. Johnston, Brit. Zooph. p. 402; 

 Allman, Ann. Nat. Hist. 1844. xiii. 330. 



PODAXINEI.— A family of Gasteromy- 

 cetous 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. 



BiBL. Montague, Ann. des Sc. nat. 2 ser. 

 XX. 69 ; Tulasne, Ann. des Sc. nat. 3 ser. iv. 

 169 ; Montague, translated in Ann. Nat. 

 Hist. vol. ix. 



PODISOMA, Link.— A genus of Cseo- 

 macei (Coniomycetous Fungi), growing upon 



Fig. 594. 



Fig. 595. 



Podisoma Juniperi. 



Fig. 594. Branch of Juniper with clavate fructification 

 protruded from beneath the bark. Nat. size. 



Fig. 595. Vertical section through a fruit, showing 

 the filaments terminating in bilocular spores. Magnified 

 50 diameters. 



the living leaves and branches of species of 

 Juniper ; the filamentous mycelium creep- 

 ing beneath the epidermis, and sending up a 

 fleshy, stalk-like, tremelloid body (fig. 594), 

 composed of agglutinated filaments (fig. 

 595), terminating in bilocular spores (or two 

 spores adherent together), each of the cells 

 having two or fom' pores, through which 

 the internal membrane is protruded in ger- 

 mination. See Uredo. 



Four species are described as British, P. 

 Juniperi- communis, P. Juniperi-Sahince, P. 

 foliicolium (on the leaves of J. communis)^ 

 and P.fuscum ; the last occurring upon Pinus 

 halepensis and J. Oxycedrus. 



BiBL. Berk.Bn^.F/or.ii.pt.2.p.362; Ann. 

 Nat. Hist. ser. 2. iii. 520; Tulasne, Ann. des 

 Sc. nat. 3 ser. xix. p. 205, 4 ser. ii. p. 186. 

 pi. 10; Fries, Summa Veg. 474. 



PODOCYSTIS, Ley. =Melampsora. See 

 Uredo. 



PODODISCUS, Kg.— A genus of Diato- 

 macese. 



Char. Frustules single or concatenate, 

 with a marginal stalk ; valves circular, con- 

 vex. Marine. 



2l 



