Pistil 
Plane of Symmetry 
Pis’til, Pisti/lum (Lat., a pestle), (1) 
the female organ of a Hower, con- 
sisting of ovary, style and stigma, 
when complete; (2) the archegonium 
of the genus Andreaea (Hooker 
and Taylor); pistilla’ceous ( + 
aceous), growing on the pistil ; 
pis’tillary, rclating to the pistil ;~ 
Cord, ‘‘a channel which passes 
from the stigma through the style 
into the ovary” (Lindley) ; pis’til- 
late, pistil/a’tus, (1) having a pistil ; 
(2) applied to a flower having pistils 
only, a female flower ; pistillif’er- 
ous, -rus (fero, I bear), bearing 
pistils ; Pistillid’ium, pl. Pistillid'ia, 
archegonia, organs analogous to 
pistils; pistillig’erous (gero, I bear), 
pistillif erous ( fero, I bear), bearing 
one or more pistils ; Pistillo’dy, the 
change of floral organs into carpels. 
Pit, (1) a small hollow or depression, 
asin a cell-wall; (2) the endocarp 
of a drupe containiug the kernel or 
seed-stone (Crozier); ~ Chamber, 
the cavity of a bordered pit on 
each side of a closing membrane. 
Pitch, a resinous exudation from the 
spruce, Picea alba, Link, ete. 
Pitch’er, a tubular or cup-shaped 
vessel, the terminal portion of a 
leaf-blade, usually containing a 
secreted digestive fluid; an as- 
cidium ; ~ shaped, campanulate, but- 
contracted at the orifice. 
Pith, the spongy centre of an exo- 
genous stem, chiefly consisting of 
parenchyma; the medulla ; ~Flecks, 
dark marks in timber due to the 
cavities made by the larvae of in- 
sects in the cambium, but at once 
filled up by cellular tissue (Hartig). 
pit’ted, marked with small depres- 
sions, punctate; used in a re- 
stricted sense for pits in cell-walls ; 
~ Ves’sels, dotted ducts, vessels 
with secondary thickenings leaving 
thinner spots. 
pitu'itous (pituita, phlegm), relating 
to mucus (Crozier). 
Pityri/asis (wlrupov, scurf) versic’olor, 
askin disease caused byMicrosporon 
Furfur, Rob, 
198 
plagiod’romous 
Placen’ta (Lat., a cake), (1) the organ 
which bears the ovules in an ovary, 
often the margin of the carpellary 
leaves; (2) in Cryptogams, the 
tissue from which sporangia arise ; 
~ shaped, placentiform; Pla’- 
centary, t a placenta which is long 
and narrow and bears many ovules ; 
Placenta’rium, placenta; Placen- 
ta‘tion, Placenta’tio, the disposition 
of the placentae; placentiferus 
(fero, I bear), bearing placentae ; 
placen’tiform, placentiform’is (for- 
ma, shape), quoit-shaped or like a 
flat cake. 
placochromat’ic (wd, mAdkos, a flat 
body, xpwyarcxes, relating to colour), 
used of Diatoms with endochrome 
in plates or disks ; ¢f. CoccocHRo- 
MATIC. 
placo’des (mAaxadys, flat), used by 
Koerber for Lichens resembling a 
rounded plate in figure. 
Plac’ophytes (7Adé, a flat body, purov, 
a plant), a term applied by Schuett 
to the Peridineae, Diatomaceae and 
Desmideae ; cf. Sac’coPpHYTES. 
(ridyios, oblique, 
dpduos; a course), applied to tertiary 
leaf-veins when at right-angles to 
the secondary veins; Plagiophoto- 
tax’y (¢2s, ¢wros, light, rdés, 
order), the oblique arrangement of 
chlorophyll gravules with regard 
to incident light(Oltmanns) ; plagio- 
phototrop’ic (rpor7, a turning), 
assuming an oblique position to 
the rays of light, as the leaflets 
of Robinia, Tropaeolum, ete., 
(Oltmanns); plagiotrop’ic, having 
the direction of growth oblique 
or horizontal; Plagiot’ropism, the 
condition described. 
plain, applied to a margin which is 
not undulate, though it may be 
sinuate (Crozier). 
plait’ed, plicate. 
plane, pla'nus (Lat.), level, even, flat ; 
Plane of Inser’tion, a plane which 
passes through the point of inser- 
tion of a lateral organ and coincides 
with the main axis and that of the 
organ ; ~ of Sym'metry, that which 
