Page:Cyclopaedia, Chambers - Supplement, Volume 2.djvu/222

 PET

PET

old difpenfatories owed the greateft part of its virtues to it. The root is the part principally ufed ; and befide thefe virtues, it has thofe of an aperient and detergent. It is prefcribed in fuppreffions of the urine and menfes, and in coughs, afthmus, and other difeafes of the breaft. See I.'utterburr. PE FASUS, among the Romans, a covering for the head, not unlike our hats ; it had a broad brim, and was ufed in jour- neys to fave the face from being fun-burnt. The pileus differed from the fetafus, as having no brim. Pitifc. in voc. See Pileus.

The petafits is obferved upon the head of antient figures of Mercury ; who wore it in the quality of the god of travel- lers and merchants. Calmet. Diet. Bibl. PETECHIAL/ewr. See catarrhal Fever. PETELMA, in the Turkifh military orders, is the procurator general of the effects of the janizaries. W hen any one dies under the protection of this body, he feals up their houfes, to fecure the tenth part of their effects ; which are due to the janizaries. Pocock's Egypt, p. 1 68. PETIA, a word ufed by medical writers in different fenfes. It is commonly underftood to mean a piece of rag, ufed to tie up medicinal ingredients in, to be ufed by infufion in liquors ; but petia oculi fignifies an haemorrhage of the eye. PETICUL^, the fame as petechia;, purple fpots appearing on

the flefh in malionant fevers. PETIGO, a word ufed by fome authors for impetigo. See the

articlee Impetigo, Cycl. PETILIUS-/3J-, a name ufed by fome botanical authors for

the African marygold. Ger. Emac. Ind. 2. PETIMBUABA, in ichthyography, the name of a fifh caught in the American feas, and called by fome, in Ejiglifh, the tobacco-pipe fifh ; a name more commonly ufed for the acui arijhteUs. See Tab. of Fifties, N°. 40. It grows to the length of three or four feet; its body is like that of an eel, long and flenderj and its mouth without teeth. The length of the nofe is confiderable, and the upper jaw is fhorter than the lower. Its eyes are remarkably large, not (mallet than a hazel nut, and Cometh ing of the fame figure. Its fkin is fmooth, like that of the eel,, and of a liver-colour on the back and fides, with feveral rows of blue fpots difpofed in three rows on the back, two on the head and one on each fide ; there are alfo fome green fpots every where interfperfed among the blue ones. The belly is white, but has forhething of a brownifh red caff, and is flat. It is a well-talted fifh. Willughhy\ Hift. Pifc. p. 234. PETIOLATE-/<?a^ among botanifts. See Leaf. PETIOLE, petiolum, among botanifts, expreffes that ftalk which fupports the leaves of a plant, as the peduncle does the frueti fications. ^

Some ufe the word petiolum to denote the whole middle rib of a leaf of any plant, which is the ftrongeft part of it and runs from the ftalk by which the leaf adheres to the tree or plant to its extremity, and from which the lateral fibres or nerves, as they are ufually called, commonly arife. The authors who have written on the fubject of the anatomy of leaves, have had occafion to be accurate about the aiftinctions of the feveral parts; and they have called this main or middle rib, the petiolus. . The fide branches going off from this, they call rami ; and the fubdivifions of thefe into more mi- nute fibres furculi : thefe generally are interwoven into a re- ticular plexus one with another, and make up the fubftance of the leaf, with the bladders of a liquid matter, which are contained in their interfttces, ' All thefe folid parts of leaves, the furculi and raw/, as well as the petiolus, are congeries of oblong fibres extended even- ly together, and collected into one body 5 and the fibres in all parts of plants are divided into two kinds ; the one con- taining juices, and called fucdf&vex the other giving paffage 1 only to air, and therefore called trachea. Lewenhoek has diftinguifhed the fucciferous veiTels into two kinds, which he calls veins and arteries : the latter, he ob- ferves, receive the fap from the root, where it is firft col lected, and carry it up to the reft of the plant, and the others bring it back again from thence, in the manner of veins. Perralt has joined a great number of experiments to Lewen- hoek's, in order to prove this fyftem of the juice veffels, but Fontenelle, and fome others, have doubted either the ex- iftence, or at leafl the ufe of the trachea: or air veffels, fup- pofing them either imaginary veffels, or deftined for other purpofes. The vine branches, however, examined either by a microfcope, or by a good eye in a good light, will fhew evidently that fuch veffels exiit, and that in very great num- bers : and the vefiels in the petiole and furculi of leaves, when ftrictly examined, are found to be of both thefe kinds. A<5t. Erudir. 1722; See Tracheae, PETIOLUS, a word ufed by botanical writers to exprefs the

ftalk of a fruit. PETIVERIA, in botany, the name of a genus of plants, the characters of which are thefe: The perianthium is compofed of three (lender, erect, obtufely-poiured leaves, and remains to inclofe the feeds., There are no petals ; the ftamina are

fix fubulated equal erect filaments, of the length of trie cup • the anthers are fimple ; the germen of the piftil is oblon^ and of a compreffed figure ; 'the ftyles are four, they are fu- bulated and f trait ; the ftigmata are fimple and permanent - the feed is fingle, of an oblong figure, narrow at the bottom broader at the top, emarginated and crowned with the ftyles which are rigid, acute, and fomewhat bent. Linnai Gen. Plant, p. 150. Plumier, Gen 39 FETOLIN, in natural hiftory, the French name for a finub of the piffachia kind, famous for affording bladders or tu- bercles on its leaves and tender branches, in the manner of the common turpentine-tree j which are found full of infects. Thefe infects are always found to be of the puceron kind, and fome of them are winged, others not, as is known to be the cafe in that genus <*f animals. Thefe bladders, and thofe of the turpentine- tree, called its horns, have been by fome fuppofed to be the natural production of the trees, but they are in reality only a peculiar fpecies of bladder-galls, formed by thefe animals, one female of which making her way into the leaf, while the young raifes its covering mem- brane into a bladder, in which (lie produces her young ones ; which by fucking its fides, derive the juices to it, and occafion its increafe. Reaumur s Hift. of Jnf. p. 34. See the article I -Puciron 7.

PETR/EA, in botany, a name given by Houfton to a genus j of plants, in honour of the name of the Lord Petre. This author, however, was guilty of an error in the characters I of this genus; for he defcribed the flower of this, and' the fruit of another very different genus, the tetracera. The j external refemblance of thefe two trees led him into the error; but Linnajus has given its characters more fully, and without any fuch miftake. They are thefe : The perianthi- um is very large and coloured; it is compofed of one leaf I divided into five obtufe expanded fegments, and remains with the fruit. The flower confifts of one leaf, and is ir- I -regular and ("mailer than the cup ; its tube is very fhort 3 its verge plain, and divided into five fegments, which are round- ifh ; and the loweft of which is larger than the others. The ftamina are four filaments, two being longer than the others, and all hid in the tube of the flower. The anthera? are fimple ; the germen of the piftil is of an oval figure ; the ftyle is fimple, and of the length of the ftamina; and the ftigmata is obtufe. The error of Houfton, in regard to the fruit, has left the world wholly in the dark as to what it really is. Linnm Gen. PI. p. 298. Heuji. Act. PETRIFACTIONS (Cycl)— The knowledge of this part of natural hiftory is but of very late years arrived at any degree of perfection. Dr. Hook, Steno, Boerhaave, and Auc*ufh'no Scilla, have been among the firft who treated judiciouflv of thefe things ; but great honour is to be done to Fabius Co- lumena, who, before the time of any of them, publifhed two admirable difcoveries upon the parts of aquatic and ter- reftrial animals, and of plants buried in the earth, and which he had himfelf feen dug up in the mountains of Andria, Apulia, and other places. He boldly declares, that thefe could be depofited there by no other means but by the general de- luge in the days of Noah ; and enters into the reafons why, in fome places, thefe remains of animal and vegetable bodies are found perfect and intire, and in others corrupted or al- tered; and obferves, that they anfwer fo exactly in every lineament to the recent bodies of the fame kind, that there can be no doubt of their having once been alfo fuch. • It is a very remarkable obfervation, in regard to the really and certainly determining the origin of petrified {hells, that they are not all alike altered by lying in "the earth, but that they differ according to the matter among which they have lain to petrify. Thus the fame fpecies of fhcll peirifyed in a loofe fand-ftone, is never nearly fo hard as when petrifyed in a folid quarry, or in a hard lime-ftone; fo that it is evident they were brought into the places where they now lie, In the irate of fhells ; and that the ftone in which they are depofited, having imparted to them its own nature, they are harder or fofter, in proportion to its hard- ■nefs. We find in pits where the fhells are depofited in loofe earth, that they are often not petrifyed at all, but rendered more foft and crumbly than before.

The echini marini, and other fuch hollow and open-mouth- ed fhells, are very often found filled up with earth or ftone, the fame with that in which they lie; and refufe matter is femetimes found among this, fuch as the fragments of other fhells, and the fpines of fome other echini. All thefe ferve to prove that the (hell, in its recent ftate, was fufpend- ed in water among fuch fubftances as thefe. And it is ' not to be fuppofed, with fome authors, that they are found originally as foflils within the fhell j fince, in this cafe, they would be fometimes doubtlefs found of f jch a tiztt as could not have got in at the mouth of the living animal ; but this is never the cafe. And upon the whole It appears very plain, that after the membranes which covered the mouths of thefe fliells in their recent ftate, were decayed or warned away, thefe extraneous bodies found entranre at them along with the marie, chalk, ftone, or whatever other

fubftance