Perfoliate. — When the stem runs through the leaf. 
Perianth. — The term Perianth was originally employed to 
designate the outer envelope or calyx of any flower, 
particularly if it was so formed as to resemble a cup. 
But it seems now to be confined in its application to 
the case of flowers having but a single envelope, of 
which it would be difficult to say, whether it is calyx 
or corolla. 
Pericarp. — The Pericarp is the exterior portion of the ripened 
ovary, of which the interior portion is the seed. It is 
regarded as consisting of three distinct parts, epicarp, 
or external integument of the fruit ; the endocarp, or 
putamen immediately investing the seed ; and the 
sarcocarp, or fleshy pulp that lies between both. You 
have them well exemplified in the peach, in which the 
outer skin is the epicarp, the fleshy pulp the sarcocarp, 
and the stone or putamen the endocarp. The base of 
the pericarp is the point where it unites with the 
peduncle; the apex, the point where the style was. 
When the fruit has arrived at maturity, some peri- 
carps open of their own accord, and discharge the 
seeds : such are said to be dehiscent. The pieces 
into which they separate, are called valves ; and the 
axis from which they separate, where a distinct axis 
exists, is called the columella. The dehiscence is 
septicidal, — that is, through the dissepiments, as in 
Rhododendron ; Loculicidal, — that is, through the 
valves, as in Lilac ; or sutural, — that is, along the 
inner edge of a single fruit or carpellum as in the pea ; 
septifragal, — that is, by a separation of the dissepi- 
ments from the valves, as in Convolvulus; or lastly, 
it is transverse to the suture of the valves, as in Ana- 
gallis. Some fruits, though ripe, remain perfectly 
closed, and do not open but on decay, or germination, 
such are said to be indehiscent. Botanists enumerate 
a great variety of modifications in the form or fabric of 
pericarps ; but they are apt to institute distinctions 
without a warrantable difference, and thus they intro- 
duce a chaos rather than a regular super-structure. 
The following species of pericarp are the most com- 
mon ; the Capsule, the Pomum, the Berry, the Nut- 
shell, the Drupe, the Silique, the Legume, the Cone. 
Perichaetium. — The Perichsetiurn is the fence or calyx of the 
mosses, being an assemblage of loosely imbricated 
scales, surrounding the fertile flowers, and terminating 
in a fine hair or bristle, as in Hypnum. 
Perigynous Insertion. — Though it seems to be admitted 
that the stamens do always originate in the base of the 
ovarium, yet botanists are in the habit of saying that 
they are inserted into the calyx or corolla, because it 
often happens that they adhere to these organs up to 
a certain point, as in Primula and in Rosa, and hence 
such insertion is said to be Perigynous. 
Peripherical. — The embryo is said to be Peripherical when 
it is accumbent on the external integuments, as in the 
grasses. 
Perisperm. — The testa of Gsertner is by some botanists deno- 
minated the Perisperm. But it does not seem to be a 
term that is at all wanted. 
Peristomium, — The fringe that surrounds the mouth of the 
capsule of the mosses is the Peristomium. It consists 
of a circular and double row of fine and tooth-shaped 
substances, sometimes united into one set, and some- 
times divided into several sets. 
Permanent. — Applied to the calyx and corolla when they con- 
tinue until the fruit is ripe. 
Petals. — The divisions of the corolla or inner envelope of the 
flower are denominated petals. They always alternate 
with the sepals or divisions of the calyx, like which 
they are either distinct or united together by their 
margins ; only they are not green, or but very rarely 
so, though they are of colours that are much more 
gaudy, — white, blue, red, or yellow. 
Petiole. — The foot-stalk that supports a leaf is very generally 
called its Petiole. 
Pinnate. — When several leaves proceed laterally from one 
foot-stalk. 
Pinnatifid. — Applied to parts cut transversely into deep ob- 
long parallel segments, 
Phytograrhy. — This term is made use of by some writers to 
denote that department of botany which describes the 
entire plant. 
Piiytology. — If we regard the term physiology as denoting 
that branch of science which treats of, and accounts 
for the phenomena of life, then it will be evident that 
it divides itself naturally into two grand departments; 
namely Zoology, involving the phenomena of animal 
life ; and Phytology, involving the phenomena of vege- 
table life. 
Pistil. — The Pis tilis a small and column-shaped, but often pestle- 
shaped organ, occupying almost invariably the centre 
of the flower, and encompassed immediately by the 
stamens, that is, when the plant is hermaphrodite. In 
monoecious and dioecious plants this arrangement can- 
not take place. The pistil is simple, as in the Cherry, 
or compound, as in the Pear ; and it is divisible at 
least into two, but very often into three distinct parts, 
namely, the ovary, the style, and the stigma. The 
ovary is the lower extremity of the pistil, supporting 
the style and stigma, and containing the rudiments of 
the future seed or seeds. [See Ovary.'] The style, or 
middle portion of the pistil, is a prolongation of the 
substance of the ovary, issuing generally from its 
upper extremity, and supporting the stigma. It is 
deciduous, and falls when the ovary is ripe ; or per- 
sistent, and adheres to the fruit. The stigma is a small 
and glandular-looking substance, crowning the style, 
and hence also denominated the summit, yet it is some- 
times, though rarely, lateral, as in Scheuchzeria. Its 
figure is globular, or hemispherical, or conical, or 
petaloid. It is destitute of an epidermis, and in its 
duration it is, like the style, sometimes deciduous and 
sometimes persistent. 
Pith. — The Pith is a soft and spongy, but often succulent sub- 
stance, occupying the centre of the root, stem, and 
branches of dicotyledonous plants, and extending in 
the direction of the longitudinal axis, in which it is 
enclosed as in a tube. In most plants it is close 
and compact, without any apparent solution of con- 
tinuity, as in the Willow and Poplar ; but in others it 
is loose and interrupted, as in the Thistle and Walnut. 
In the Fig andElderits diameter is large in proportion 
to that of the stem or branch ; while in the Oak or 
Elm it is but very small. 
Placenta. — That portion of the ovarium in which the ovula 
originate is called the Placenta. It generally occupies 
the whole or a portion of one angle of each cell, being 
formed by the union of the folded-in margins of the 
carpellary leaf. 
Plaited. — Lying in folds like a fan. 
Plant. — A plant or vegetable is a living and organized body, 
insentient, and incapable of locomotion ; but origi- 
nating in a seed which springs up into a plant, again 
producing seed 
Pltalet.— The Piantlet is that portion of the embryo which 
is invested, or partially invested, by the cotyledons ; 
being the future plant in miniature. 
Plumous. — Having a feathery appearance. 
Pollen. — The pollen is the fine powder that is contained in 
the anthers or summit of the stamens. 
Pollen Tubes. — The Pollen tubes, which are equivalent to 
the boija'u. v of M. Ad. Brongniart, are tubes of an 
extreme tenuity, which issue from the innermost of 
the two membranes that invest the globule of pollen. 
Polygamous Plants. — Plants producing male, female, and 
hermaphrodite flowers, indifferently, are said to be 
polygamous. 
