plerome 
inf-nts at the growing-points of the axis of 
plants. 
Enclosed by thli [the perlhlem ) It * central cellular mass, 
oat of which Ihe fibro- vascular bundle! and the structures 
of the central part of the shoot or root are formed ; tlii* 
luu been termed plerone. Jfneye. Brit. , I V. tfi 
plerome-sheath (ple'rom-sheth), . In >><>L. 
a limiting layer of surrounding cellular tissue 
which incloses onlinarily a group of fibrovas- 
ciilar Immlles: with some authors the same as 
lnnidli--xhi<ith. 
pleromorph (ple'ro-mdrf), i. [< Gr. irsf/pa/to, 
ii tilling up, T tu'iw, form.] A kind of pseudo- 
niorpli formed by the filling of a cavity left by 
the removal of a crystal of gome species with 
another mineral or mineral substance. 
plerophoria (ple-ro-fo'ri-a), . [NL.] Same as 
pleropfiory. 
plerophory(ple-rof'o-ri), H. [< NL.plerophoriii, 
< Gr. T!'t.ri\x>yopiii, full conviction, certainty, < rr)j/- 
piMfnprlv, give full satisfaction or certainty, in 
puss, be fully convinced, < irAq/ir^, full, + ^epeiv 
= E. bear 1 .] Full persuasion or confidence; 
perfect conviction or certitude. [Rare.] 
Young men apprehend not the necessities of knowledge, 
old men presume of a plemphory and abundance. 
Ret. T. Adam*, Works, I. 317. 
Abraham had a plerophory that what was promised Cod 
was able to perform. Barrtnc, Sermons, 1 1. iv. (Latham.) 
The plerophory or full assurance of faith. 
He/in/, Christ and Christianity, p. 8. 
plesancet, plesauncet, . Obsolete forms of 
iileaxance. 
_ esantt, plesauntt,. Obsolete forms of pleag- 
tlllt. 
plesht, . An obsolete variant of plaxhi. 
Plesiarctomys (ple-si-ark'to-mis), i>. [NL., < 
(Jr. ir'/.iioiot, near, + NL. Arclomyx, q. v.] A 
Miocene genus of sciuromorphic rodents, some- 
what resembling marmots. 
Plesiochelyidae (ple'si-o-ke-H'i-de), . pi. 
[NL., < Plexiochelys + -idse.~\ A family of pleu- 
rodirouH turtles, typified by the genus Plexio- 
chelys. They were distinguished by the total absence of 
the mesoplastral element in the plastron and the union of 
the pnbis above with the eplplastral. They were of Mesc- 
luic age. 
Plesiochelys (ple-si-ok'e-lis), . [NL., < Gr. 
T^/.r/aiof. near, + jtavf, a tortoise.] An extinct 
genus of turtles, typical of the family Plenio- 
chcli/itlje. 
plesiomorphic (ple'si-o-mor'fik), . [<pleirio- 
morph-oitx + -ic.J Same as plestomorphoiu. 
plesiomorphism (ple'si-o-m&r'fizm), n. [<]>lr- 
siomorph-oug + -im.] In cryxtal., the relation 
of crystallized substances the forms of which 
closely resemble each other, but are not abso- 
lutely identical. 
plesiomorphous (ple'si-o-mor'fus), . [< Gr. 
x'/qoios, near, + //<>p^y, form, + -ous.'] Nearly 
alike in form; exhibiting plesiomorphism. 
Plesiopidae (ple-si-op'i-de), . pi. [NL.,< Plr- 
iopg + -idte.] A family of acanthopterygian 
fishes, typified by the genus Plexiops, generally 
embraced in the family I'xeurtochroniiditlse. 
Plesiops (ple'si-ops), . [NL., < Gr. x>j>oios, 
near, + <Ji,". eye, face.] A genus of pseudo- 
4554 
dominal rilm are present. The skull has a tlxed quadrate 
bone, one posUirbltal bar, and no free parocclplta.1 ; the 
rertebrw are amphkoelous, with nenrocrntral sutures, and 
only two of them compose a sacrum. The ribs are one- 
headed. The eyeball has no sclerotic ring of Nines, and 
the teeth are socketed In a single row in both jaws. The 
order contains many genera of gigantic fish-like aaurians 
from tlie Trias, Lias, and Chalk, whose affinities are with 
the chelonians, notwithstanding the wide difference In 
form. The order is also called Sattrtijiteriiyia, but Pleno- 
Mwria is its prior and proper name. .See cut under Vie. 
ftuMtaurut. 
plesiosaurian (ple'si-o-sa'ri-an), a. and n. [< 
1'leninMitirin + -an.] 1. a. Of" or pertaining to 
the Plesiosauria; plesiosauroid; sauroptcrygian. 
II. n. A member of the Pleviomturia ; a plesi- 
osaur. 
Plesiosauridae (ple'si-o-sa'ri-de), n. pi. [NL,., 
< Pleaiosaurus + -idee.] A family of gigantic 
animals represented by the genus Plesiosauru* 
and related forms, having both fore and hind 
limbs perfectly natatory. The pterygoida diverge 
backward, and do not overlie the basisphenoid, and there 
are small infra-orbital vacuities In the palate. They lived 
from the uppermost Triasslc to the Cretaceous epoch. 
Some of the species were of huge dimensions. 
plesiosauroid (ple'si-o-sa'roid), . [<pUsiosaur 
+ -"/'/.] Kesembling a plesiosaur; plesiosau- 
rian. Oven. 
Plesiosaurus (ple'si-o-sa'rus), n. [NL. (Cony- 
beare), < Gr. K/qoiof, near, + oaiipof, lizard.] A 
chromidoid fishes, regarded by gome as the type 
of a family PleniojiiiUe. It contains fishes of tne 
Indian and Pacific oceans, as /'. Mrrkrri. 
plesiosaur (ple'si-o-sar), . An animal of the 
iinli-r Plcxinxniiria. 
Plesiosauri (ple'si-o-sA'ri), . pi. [NL., pi. of 
PlMJOtavriie.] Same as Plesiosauria. 
Plesiosauria(ple'8i-o-sa'ri-a),n.j>,'. [NL.: see 
PlMtaMwm*.] An order of extinct marine /.'</ 
tilia, having the limbs fitted for swimming, the 
body fish-like, the neck long, and the head iju id- 
small. The fore and hind limbi both constltuteflippers 
or paddle* like those of cetacean mammals, having niirner 
ous phalange* Inclosed In a common Integument like a tin. 
The pectoral arch Is complete, with trlradtate scapular 
and large coracoiii and clavicular elements, and the pelvis 
Is large, with separate Ilium, Ischlnm. and publ*. There Is 
no sternum, nor are there any sternal ribs, but flouting ab- 
Skeleton of PlesioiaHrus, with diagrams of the more important 
parts. 
A. skull : A'0, nasal aperture ; Pttix. premaxilla. B. left fore limb : 
//. htimerus ; A', V, radius and ulna ; r. i t tt. radiale. iintennedium, 
and iilnare of carpus; I. 7, 3, distal carpalia ; Me, metacarpus; PH. 
Rh.ilaiwes. C. dorsal vertebra, with A', ribs, ami t^O, ventral o&sifka- 
ons; (, centrum ; N.I. neural arch. I), left hind limb: /'. femur; 
/ , tibia ; f, fibula ; t, i, /, tibi.de. intermedium, and filiulare of tar- 
sus ; i. a, 3, distal tarsalia ; Mr, metatarsus; 1'ti, phalanges. 
genus of Keptilia, typical of the order Plesio- 
sauria, and formerly conterminous with it, now 
restricted to forms from the Upper Triassic 
(Uhtetic) and the Liassic, as /'. dolicliodirtis, 
with extremely long neck. 
plesiret, A Middle English variant of plea- 
sure. 
plessimeter (ple-sim'e-ter), n. Same as plex- 
imeter. 
plet (plet), w. [Also plete, plitt; < Buss, pletu, 
a whip.] A whip, especially one of the form 
used by the Russian penal administration for 
the chastisement of refractory prisoners. 
There is another flagellator, however, called the plete, a 
whip of twisted hide, which Is still retained at a few of 
the most distant Sil>eru\n prisons, and only for the most 
Incorrigible, on whom irons, the birch, ana other punish- 
ments nave had no effect. Encyc. Brit., XIX. 762. 
plete 1 !, f. A Middle English form of plead. 
plete 2 , . See plet. 
pleteret, . A Middle English form of pleadei: 
plethora (pleth'6-rS), H. [Formerly also pleth- 
ory; = F. plcthore = Sp. pletora = Pg. plethora 
= It. pletora, < NL. plethora, < Gr. irtrfajpii, full- 
ness, in med. plethora, < w?>Jflof, fullness, < ->>/- 
Bttv, be or become full, < ^irty in m/iir/tdva/, fill, 
T'-^W, li.pleiius, full: see/a/fl, plenty.] 1. In 
p<itlil., overfullness of blood; a redundant full- 
ness of the blood-vessels. . 
At the same time he is full and empty, bursting with a 
jfelliury, and consumed with hunger. 
Jer. Taylor, Works (ed. 1836), I. 810. 
Vi.nr character at present Is like a person In a plethora. 
absolutely dying from too much hi vilth. 
Sheridan, School for Scandal. Iv. . 
2. Ov.-rfiillncss in any respect; superabun- 
dance. 
A pteUiora of dull fact Is ... especial!) the character- 
istic of . . . |thls| volume on ancient history. 
Atheiurum, Jan. 7, 1888, p 11. 
pleuracanth 
plethoretic (pleth-9-ret'ik), . [< plethora + 
-etic, as in diuretic, etc.] Same as plethoric. 
plethoretical (pleth-p-ret'i-kal), a. [< pliilm- 
retic + -at.] Same as plethoric. 
plethoric (ple-thor'ik or pleth'o-rik), a. [< Gr. 
-'/ i/HapiKof , ( Tr/u/Oupq, plethora: see pletSora.} 
Having a full habit of body, or the vessels over- 
charged with fluids; characterized by plethora, 
in any sense. 
And late the nation found, with fruitless skill, 
Its former strength was but plethoric 111. 
OMsmitli, Traveller, 1. 144. 
At length he broke out Into a plethone fit of laughter 
that had well nigh choked him, by reason of his excessive 
corpulency. Jmng, Sketch-Book, p. 1. 
The pocketn, plethoric with marbles round, 
That still a space for ball and pegtop found. 
Lowell. Blglow Papers, 1st ser.. Int. 
plethorical (ple-thor'i-kal), a. [< plethoric + 
-al.] Same as plethoric. 
plethorically (ple-thor'i-kal-i), adv. In a ple- 
thoric manner ; with plethora. 
plethoryt (pleth'o-ri), . An obsolete fonn of 
plethora. 
Plethospongiae (ple-tho-spon'ji-e), n. pi. fNL., 
< Gr. Tr/./yftjf, fullness, -f- oird)jof, sponge.] In 
Sollas's classification of sponges, same as-Micro- 
mastictora. 
plethron, plethrum (pleth'ron, -rum), n.; pi. 
plethra (-ra). [< Gr. irZeSpov (see def.).] In 
ancient Greece, a fundamental land-measure, 
being the square of 100 feet, or 10,000 square 
feet. As a measure of length, the plethron was the side 
of this square, the sixth part of a stadium, or about 101 
English feet. 
plethysmograpb. (pie-tins' mo-graf), n. [< Gr. 
ir/.ilOro/toc,, increasing, enlargement (< irr.ifli'tiv, 
be or become full, ovIqMMtv, make full, < irUjfof, 
irlyOi't, fullness), + fpdfeiv, write.] An instru- 
ment for obtaining tracings indicating the 
changes in the volume of a part of the body, 
especially as dependent on the circulation of 
blood in It. The part, as the arm, is Inclosed In a tight 
vessel and surrounded by water, which is forced up or al- 
lowed to recede in a tube as the volume increases or di- 
minishes. 
plethysmographic (ple-this-mo-graf'ik), a. [< 
plethuatnograph + -ic.] Of or pertaining to 
the plethysmograph, or its use. Medical Xeicx, 
XLIX. 276. 
pletingt, . A Middle English form of pleading. 
pletourt, . A pleader; a lawyer. 
plough, pleuch (pluch), t. and f. Scotch forms 
of ploir. 
pleugh-paidle (pluch 'pa'dl), n. A plow-staff. 
Scott, Old Mortality, xxxv. [Scotch.] 
pleura 1 (plo'rii), .; pi. pleurx (-re). [NL., < 
Gr. irfavpa, a rib, in pi. (also in sing.) the side, 
side of a triangle, a page of a book ; cf . neut. 
ir/tvpAv, a rib, pi. Tr'Acvpa, the ribs, the side.] 1. 
The principal serous membrane of the thorax ; 
the shut sac, having a serous surface, which 
lines the walls of the chest, and is reflected over 
the surface of each lung. There are two pleura, 
right and left, completely shut off from each other. Each 
Is divided into a parietal or costal layer and a visceral 
or pulmonary layer. (See the phrases below.) Like the 
other serous membranes, the pleura- are moistened with 
a serous secretion, which serves to facilitate the move- 
ments of the lungs in the cheat. See cuts under perito- 
neum and thorax. 
2. In conch., one of the lateral tracts on each 
side of the rachis of the lingual ribbon of the 
odontophore : generally used in the plural. 
The teeth of the pleura are termed nnclnl : they are ex- 
tremely numerous in the plant-eating gastropods. 
Woodtmnl. 
3. In compar. anat., the lateral portion of one 
of the rings composing the integument of an 
arthropod or articulate animal, lying between 
the tergum and sternum, and in insects and 
crustaceans consisting of two pieces, the epi- 
meron and episternum. In dencriptlv. .tii,,m,,|, c> 
the term Is generally restricted to Ihe side of the thorax, 
as In Diptera. Cavity of the pleura, the space between 
the parietal and pulmonary layers of the pleura. In 
the normal state these layers are in contact. See cut 
under thorai. - Parietal pleura, (a) Same as pleura 
eottalu. (b) All the parts of the pleura cxcejit I)H jml 
monary portion. Pericardia! pleura. See pericarjial. 
- Pleura costalis. the costal part of the nlcnm, lining the 
walls of the thorax . Pleura mediastmalls, Hut p:m 
of the pleura which enters into the format Ion of the medi- 
astinum. Pleura pericardlaca. Same as pericanlial 
pleura. Pleura phrenica, Hut part of thepl<m:i which 
invests the upper surface of the diaphragm : the dia- 
phragmatic pleura. Pleura pulmonalis, the pulmo- 
nary or visceral part of the pleura. Investing the lnii|i. 
Visceral pleura, On- pleura pulmonalis. 
pleura' 12 , ". Plural of /ileuron. 
pleuracanth (plo'ra-kanth). a. and . |< NU 
I'll iii'iii-iiiiHnin. | Same as plriiracmithinil. 
