POLYPODTOIDE^. 



[ 525 ] 



POLYSIPHONIA. 



on the anastomosing venules. Venules ana- 

 stomosing in irregular hexagonal spots. 



*** Veins anastomosing, with free veins in 

 the areolce. 



VI. NiPHOBOLUS. Sori globose, seated 

 on the apex of the venules. Venules very 

 much branched, forming transverse rhomboid 

 spots; secondary venules arising from the 

 transverse venules, and bearing the sori at 

 their apices. 



VII. Dryostachium. Sori quadran- 

 gular, seated on the apex of the venules. 

 Venules very much branched, forming some- 

 what quadrangular meshes. Secondary 

 venules very numerous, variously divergent, 

 and bearing the sori at the apex. 



POLYPODIOIDE^.— A tribe of Poly- 

 podiaceous Ferns, of large extent, broken up 

 iato subtribes and genera, which are cha- 

 racterized by peculiarities generally requiring 

 a more or less powerful lens to distinguish 

 them. In certain cases, where the venation 

 of the leaves, and the relation of this to the 

 fructifying points, are in question, it is found 

 very convenient to scrape off the sori of pin- 

 nules and place them in spirits of tuiiicntine 

 or oil, between two shps of glass, for exami- 

 nation with a low power under the micro- 

 scope by transmitted light. The general 

 arrangement of the sori, with the indusium, 

 in very minute forms, is best observed as an 

 opaque object, with a low power, and a 

 lieberkuhn or side condenser ; if held in the 

 mounted forceps, the pinnule can be turned 

 about and thoroughly examined. 



Synopsis of the sub-tribes. 

 A. Sori without indusia. 



I. AcROSTiCHE^. Sori seated on all the 

 veins, venules, and parenchjina. 



II. GYMNOGKAMMEiE. Sori scatcd on 

 the backs of all the veins and venules. 



III. Polypodies. Sori globose, only 

 on certain arms of the veins. 



IV. MENisciEiE. Sori kidney-shaped, 

 seated only on certain arms of the veins. 



V. Gramitides. Sori linear, seated 

 only on certain arms of the veins. 



VI. TsNiTiDEs. Sori linear, in pairs 

 on either side of the rib, parallel, continuous. 



B. Sori with indusia, 



VII. AspiDiES. Indusium orbiculate, 

 peltate. 



VIII. DiPLASiEs. Indusium linear or 

 oblong, fixed longitudinally in the middle. 



IX. Nephrodies. Indusium cordate, 

 affixed at the notch. 



X. Cystopterides. Indusium tongue- 

 shaped, fixed by the lower point. 



XL LiNDSSEiE. Indusium linear, 

 elongated, free outside. 



XII. AsPLENiEs. Indusium elongated, 

 fixed at the side, free within. 



XIII. Pterides. Indusium Unear, fixed 

 at the side, free within. 



XIV. ScoLOPENDRES. Indusium linear, 

 flat, margins free, opposite. 



XV. Davallies. Indusium somewhat 

 urn-shaped, dehiscing externally at the apex. 



POLYPODIUM, Linn.— A genus of Ferns 

 with naked sori, of which there are several 

 indigenous representatives ; P. vulgare^ the 

 Oak-Fern, being one of our commonest spe- 

 cies. Exceedingly well adapted for examina- 

 tion of the structure of sori and sporanges 

 in this familv. 



POLYPOREL— A family of Hymenomy- 

 cetous Fungi, characterized by bearing basi- 

 diospores clothing tubes, pores or pits, on 

 the under side of a stalked or sessile pileus, 

 or fleshy cap or disk. The basidiospores are 

 seen by horizontal sections from the under- 

 sm-face of the pileus. (See Basidiospores 

 and Hymenomycetes.) 



BiBL. Berkeley, On the Fructification of 

 Ilymenomycetous Fungi, Ann. Nat. Hist. i. 

 81; Leveille, Sur V Hymenium des Champi- 

 gnons, Ann. des Sc. nat. 2 ser. viii. 324. 



POLYSELMIS, Duj.— A genus of Infu- 

 soria, of the family Euglenia. 



Char. Oblong or variable in form, Tvith 

 several anterior flagelliform filaments, and 

 a single red e3'e-spot. 



Probably the zoospore of a Confervoid 

 Alga. 



P. viridis (PI. 24. fig. 68) resembles a 

 Euglena of an oblong form with the ends 

 rounded ; one of the filaments is longer than 

 the three or fom' others which smTound its 

 base. Aquatic; length 1-650". 



BiBL. Dujardin, J«/m5. p. 370. 



POLYSIPHONIA, Grev.— An extensive 

 genus of Rhodomelacese (Florideous Algse), 

 with cylindi'ical, more or less articulated 

 fronds, the joints consisting of a circle of 

 longitudinally arranged cells surrounding a 

 central cell (hke the wood-bundles of a 

 young Dicotyledonous stem surrounding the 

 pith), so that the transverse section presents 

 the appearance of a rosette ; the number of 

 peripheral cells varies among the 300 dif- 

 ferent species of this genus, from four to 

 twenty-five. The British forms have four 



