USED IN NATURAL HISTORY. 



115 



young branch. Applied to the 

 lower part of a petiole, when it 

 sheathes the branch. 



PERICHJB'TIUM. fr. gr. chaite, seta, 

 a hair. Applied to the peculiar 

 leaves which surround the base 

 of the seta, or stalk of the spo- 

 rangium or seed-vessel of mosses. 



PERICLI'IUUM. fr. gr. kline, a couch. 

 Cassini's name for the involucrum 

 of composite plants. 



PE'RIDOT. Prismatic chrysolite, (p. 

 121, Book viii). 



PE'RIGOX. ) fr. gr. peri, around ; 



PERIGO'NIUM. geinomai, I grow. 

 A floral envelope, which partakes 

 of the nature both of calyx and 

 corolla. 



PERIGY'NOXJS. fr. gr. peri, around ; 

 gune, pistil. Surrounding the pis- 

 til. 



PERIO'STRACUM. fr. gr. ostrakon, a 

 shell. The epidermis, or mem- 

 brane analogous to scarf-skin, 

 which covers certain shells. 



PERIPO'LYGOU. A prism with very 

 numerous faces. 



PE'RI SPERM. fr. gr. peri, around ; 

 sperma, seed. Another name for 

 the albumen of the seed of plants. 



PERISTA'MINE.E. Name of a class 

 of plants. 



PERISTO'MIUM. fr. gr. stoma, the 

 mouth. Peristome. The mem- 

 brane, or series of tooth-like pro- 

 cesses, which closes the orifice of 

 the theca of mosses. 



PERITHE'CIUM. fr. gr. thece, a case. 

 Perisporium. Peridium. The case 

 which contains the reproductive 

 organs of certain fungi. 



PERITONEUM. fr. gr. peri, around ; 

 teino, I stretch. A serous mem- 

 brane which lines the abdominal 

 cavity, and covers, entirely or in 

 part, all the organs contained in it. 



PERITRE'MA. fr. gr. trema, a hole. 

 The raised margin which sur- 

 rounds the breathing -holes of 

 scorpions. 



PERITRO'PAL. fr. gr. trepo, I turn. 

 Applied to the embryo of the 



seed of plants when it is directed 

 from the axis to the horizon. 



PE'RLITE. Pearl stone, a gray va- 

 riety of obsidian. 



PER'MANKNT GAS. Any gas which 

 remains in the aeriform state un- 

 der ordinary circumstances. Any 

 part of a plant is said to be per- 

 manent when it remains longer 

 than is usual for similar parts in 

 most plants. 



PERMEABILITY. That property of 

 certain bodies by which they ad- 

 mit the passage of other bodies 

 through their substance. 



PER'MIAIT. After the ancient king- 

 dom of Permia. A name ap- 

 plied by Mr. Murchison to a sys- 

 tem of rocks, consisting of an 

 extensive group of fossiliferous 

 strata, intermediate in their geo- 

 logical position, between the car- 

 boniferous and triassic systems, 

 the latter being the upper portion 

 of the New Red Sandstone for 

 mation. 



PE'RNA. Lat. A gammon. A ge- 

 nus of the family of ostracea. (p. 

 75, Book v). 



PE'RN^E. Lat. plur. of perna. 



PE'RNIS. fr. gr. pernes, a certain bird 

 of prey. The generic name of 

 the honey-buzzards. 



PE'ROXATE. fr. lat.pero, a high shoe. 

 In botany, applied to the stipes of 

 fungaceous plants, when thickly 

 laid-over with a wooly substance, 

 ending in a sort of meal. 



PERO'XIDE. The highest degree of 

 oxidizement of which a metal 

 or other substance is susceptible 

 without becoming an acid. 



PE'RSICA. Lat. Persian. 



PERSI'STENT. Permanent. Not fall- 

 ing at the usual period. 



PE'RSOXATE. fr. lat. persona, a mask. 

 A form of corolla, which has the 

 mouth closed by a prominent pa- 

 late, (fig. 91, p. 74, Book vii). 



PERTU'SSUM. Lat. Broken, cracked. 



PES-PELICA'NI. Lat. Pelican foot. 



PE'TAL. fr. gr. petalon, leaf. A part 



