EXPLANATION OF TERMS

[The following simple definitions of the more common terms used have been mostly taken or adapted from the works of Asa Gray and others, and will prove useful to those unacquainted with botany, or to those whose memories require refreshing.]

ROOTS

The root is that portion of the plant which grows downward, fixing it to the soil, and absorbing nourishment from the latter. True roots produce nothing but root-branches or rootlets.

Simple or unbranched roots are named according to their shapes—

conical, when like the carrot;

napiform, when like the turnip;

fusiform, when like the long radish.

Multiple, or branched, roots may be—

fascicled, or bunched, as in the dahlia;

tubercular, when furnished with small tubers;

fibrous, when threadlike.

STEMS

The stem is the ascending axis of the plant, which usually bears the leaves, flowers, and fruit. The points on the stem to which the leaves are fastened are called the nodes; and the portions of stem between the nodes are called the internodes. The angle formed by the upper side of the leaf and the stem is called the axil.

Stems aboveground are classed as—

erect, when growing upright;

procumbent, when lying on the ground without rooting;

decumbent, when lying on the ground with the tip ascending;

diffuse, when loosely spreading;

creeping, when growing on the ground and rooting.

Stems underground are classed as rhizomes (or rootstocks) tubers, corms, and bulbs, the forms passing into one another by gradations.

A rhizome, or rootstock, is a horizontal underground stem. It is sometimes thick, fleshy, or woody, as in the iris;

a tuber is a short, much thickened rootstock, having eyes or buds of which the potato is an example;

a corm is a depressed and rounded, solid rootstock; it may be called a solid bulb; the garden cyclamen is an example;

a bulb is a leaf-bud, commonly underground, with fleshy scales or coats; the lily is an example.

LEAVES

Leaves are the green expansions borne by the stem, out-spread in the air and light, in which assimilation is carried on. They may be said to be the stomachs of the plant. A typical leaf consists of three parts—the blade, the foot-stalk (or petiole), and a pair of stipules. Yet any one of these parts may be absent.

The blade is the expanded portion of the leaf and the part to which the word leaf, in its commonest sense, is applied;

the stipules are small, usually leaflike bodies borne at the base of the petiole, usually one on either side;

the petiole is the stalk of the leaf.

Leaves are simple, when having but one blade; compound, when having more than one, when each blade is called a leaflet.

Compound leaves are said to be—

pinnate, when the leaflets are arranged along the sides of a petiole, or rather of its prolongation, the rachis;

abruptly pinnate, with an even number of leaflets;

odd-pinnate, with an odd leaflet at the end;

palmate, or digitate, when the leaflets all diverge from the summit of the petiole, like the fingers of a hand.

VENATION

The venation, or veining, of leaves relates to the mode in which the woody tissue, in the form of ribs, veins, etc., is distributed in the cellular tissue.

There are two principle modes—

the parallel-veined, of which the iris is an example;

the reticulated-veined, or netted-veined, of which the Elm is an example.

Small veins are called veinlets.

FORM

As to general form, or outline, leaves are:—

Those broadest in the middle—

peltate, or shield-shaped, when rounded, with the stem attached to the center, or near it—as in the garden nasturtium;

orbicular, when circular in outline, or nearly so;

oval, when having a flowing outline, with the breadth considerably more than half the length, and both ends alike;

elliptical, when having a flowing outline, twice or thrice as long as broad, and both ends alike;

oblong, when nearly twice or thrice as long as broad;

linear, when narrow, several times longer than wide, and of about the same width throughout;

acerose, when needle-shaped—like the Pine.

Those broadest at the base—

deltoid, when having the triangular shape of the Greek letter delta;

ovate, when having an outline like the section of a hen's-egg, the broader end downward;

lanceolate, or lance-shaped, when several times longer than broad, and tapering upward, or both upward and downward;

subulate, when shaped like an awl;

cordate, when ovate, with a heart-shaped base;

reniform, when like the last, only rounder and broader than long;

auriculate, when having a pair of small blunt projections, or ears, at the base;

sagittate, or arrow-shaped, when those ears are acute and turned downward, the body of the leaf tapering upward;

hastate, or halberd-shaped, when the ears or lobes point outward.

Those broadest at the apex—

obovate, when inversely ovate;

oblanceolate, when inversely lanceolate;

spatulate, when rounded above, and long and narrow below, like a druggist's spatula;

cuneate, or wedge-shaped, when broad above, tapering by straight lines to an acute base;

obcordate, when inversely cordate.

Sometimes no one of the above terms will describe a leaf, and it becomes necessary to combine two of them; as, linear-spatulate, ovate-lanceolate, etc.

THE APEX

Leaves are classified according to their apices; as—

emarginate, when having a decided terminal notch;

truncate, when abruptly cut off;

obtuse, when ending in a blunt or roundish extremity;

acute, when ending in an acute angle, without special tapering;

acuminate, when tapering into a narrow, more or less prolonged end;

mucronate, when abruptly tipped with a small, short point.

THE MARGIN

Leaves are classified according to their margins; as—

entire, when the margin is completely filled out to an even line;

repand, or undulate, when the margin is a wavy line;

dentate, or toothed, when the teeth point outward;

crenate, or scalloped, when dentate, with the teeth rounded;

serrate, when having small sharp teeth directed forward;

incised, when cut by sharp and irregular incisions more or less deeply;

lobed, when cut not more than half-way to the midrib, and the divisions or their angles are rounded;

cleft, when cut half-way down or more, and the lobes or sinuses are narrow or acute;

parted, when the cutting reaches almost but not quite to the midrib;

divided, when the blade is cut into distinct parts, thus making the leaf compound.

All these terms may be modified by the words pinnate or palmate; thus—pinnately parted, pinnately divided, palmately parted, palmately divided, etc.; also by the adjectives once, twice, thrice, etc.

TEXTURE

Leaves vary as to texture, and may be—

coriaceous, or leathery;

succulent, or juicy;

scarious, or dry and thin;

fleshy, or thick;

herbaceous, or thin.

ARRANGEMENT

According to their arrangement on the stem, leaves are—

alternate, when distributed singly at different heights on the stem;

opposite, when two stand opposite each other at the nodes;

whorled, when more than two are borne at a node, equidistant in a circle around the stem.

INFLORESCENCE

Inflorescence is a term commonly applied to the mode of flowering—i.e. to the arrangement of blossoms on the stem and their relative positions to one another.

A peduncle is the stem of a solitary flower, or the main stem of a flower-cluster;

a scape is a peduncle growing from the ground;

a pedicel is the stem of each flower in a cluster;

a bract is a small floral leaf;

an involucre is a collection of bracts around a flower-cluster or around a single flower.

Flowers may be solitary or clustered.

Solitary flowers or flower-clusters are—

terminal, when borne at the summit of the stem;

axillary, when borne in the axils of the leaves.

A flower-cluster is called—

a raceme, when the flowers are arranged along the axis upon pedicels nearly equal in length;

a corymb, when the flowers are arranged as in the raceme, with the lower pedicels elongated, making the cluster flat-topped;

an umbel, when the pedicels arise from the same point, like the rays of an umbrella, and the cluster is flat-topped;

a panicle, when compound, irregularly made up of a number of racemes;

a spike, when like a raceme, the flowers being without pedicels;

a spadix, when it is a fleshy spike, generally enveloped by a large bract, called a spathe, as in the calla-lily;

an ament, or catkin, when it is a pendent spike, with scaly bracts, like the Willow;

a head, when it is a shortened spike, with a globular form;

a cyme, when it is branched and flat-topped, usually compound, with the older flowers in the center of each simple cluster.

THE INDIVIDUAL FLOWER

A complete flower consists of stamens and pistils (the organs of reproduction), and calyx and corolla (the floral envelops which protect the stamens and pistils). But any one of these organs may be absent.

The calyx is the outer floral envelop, which is more often green, though it is sometimes colored. It may consist of a number of separate parts, called sepals, or these may be more or less united.

The corolla is the inner floral envelop. It is usually colored, and forms the most beautiful feature of the flower, and plays an important part in attracting insects to it, which may carry on the work of fertilization. It may consist of a number of separate parts, called petals, or these may be more or less united, in which case the corolla is said to be gamopetalous. When the calyx and corolla are much alike, and seem like one floral circle, this is referred to as a perianth.

The stamens and pistils are called the essential organs of a flower, because they are necessary to the maturing of the fruit.

Perfect flowers have both sets of essential organs.

Imperfect flowers have but one set of essential organs.

Staminate (or male) flowers have only stamens;

Pistillate (or female) flowers have only pistils.

Neutral flowers have neither.

THE STAMEN

The stamen consists of two parts—the filament and the anther. The filament is the stalk of the stamen. The anther is the little case holding the pollen, or powdery substance, which, falling upon the stigma, is conducted downward into the ovary, where it quickens the ovules into life. The anther normally consists of two cells, which more often open lengthwise for the discharge of the pollen, though they sometimes open by terminal pores or chinks, or by uplifting lids.

Stamens sometimes undergo a morphological change, taking the form of scales or other bodies (as is the case in many of our Brodiæas), when they are called staminodia.

THE PISTIL

The pistil is the organ occupying the center of the flower. It consists of three parts—the ovary, or the enlarged part below, consisting of one or more cells or cavities, and containing the ovules, or unfertilized seed; the style, or the stem which upholds the stigma; the stigma, or the roughened portion which receives the pollen.

The pistil is simple, when it has but one ovary, style, stigma, etc.; compound, if any one of these is duplicated.

THE FRUIT

The fruit is the ripened ovary. After the ovules have been fertilized, the ovary is called a pericarp. Fruits may be either fleshy or dry.

The following are some of the principal kinds of dry fruits:—

A capsule is a dry, dehiscent (splitting) fruit, composed of more than one carpel or division;

an akene is a small, dry, hard, one-celled, one-seeded indehiscent fruit;

a follicle is a pod formed from a single pistil, dehiscing along the ventral suture only;

a legume is a simple pericarp, opening by both seams.

a samara is a dry, indehiscent fruit, having a wing.

The following are some of the principal kinds of fleshy fruits:—

A pome is a fruit like an apple or pear;

the pepo, or gourd, fruit is like that of the melon, squash, etc.;

the drupe is like that of the cherry, plum, and peach;

the berry is like that of the grape, currant, and tomato.

Aggregate fruits are those in which a cluster of carpels, all of one flower, are crowded upon the receptacle into one mass; as in the raspberry and blackberry.