BOTANY. 
white flowers, and a tender eatable pod, 
called the top-knot pea, in which this va- 
riety of stem is regularly propagated by 
seed. 
2. Culmus, a straw, or culm, fig. 10, is 
the peculiar stem of grasses, rushes, and 
such like plants. It bears both leaves and 
flowers, and in that respect comes under 
the denomination of a caulis; but is readily 
known by its habit, though difficulties at- 
tend its definition. In most grasses, corn, 
&c. it is jointed in a manner peculiar to it- 
self, and then cannot be mistaken ; but in 
common rushes, and some few grasses, it is 
destitute of joints. When these parts are 
bent, it is called geniculate, and such joints 
readily take root. 
3. Scapus, a stalk, fig. 11 , springs imme- 
diately from the root, bearing flowers and 
fruit, but not leaves, as in the primrose and 
cowslip. It is either simple or branched, 
naked or scaly. In the cyclamen it be- 
comes spiral after flowering, and buries the 
seeds in the ground. Dr. Smith has found, 
contrary to the opinion of Linnaeus, that a 
plant may sometimes be increased by its 
scapus, as in laclienalia tricolor, which oc- 
casionally bears bulbs on its stalk. 
4. Pedunculus, the flower-stalk, fig. 12, 
springs from the stem or branches, bearing 
flowers and fruit, but not leaves. Pedicellus 
is a partial flower-stalk, or, in other words, 
the ultimate subdivision of a general one. 
The most common situation of a flower- 
stalk is axillary, originating from between a 
leaf and the stem, or between a branch 
and the latter. It is rarely opposite to a 
leaf, as in some species of geranium, and 
still more rarely intermediate between two 
leaves, as in some kinds of solanum. It is 
either terminal or lateral : solitary, cluster- 
ed, or scattered; simple or branched. Ac- 
cording to the various modes in which it is 
subdivided several kinds of inflorescence 
are distinguished, to be mentioned hereafter. 
Sessile flowers are such as have no stalk. 
The flower-stalk is occasionally naked, or 
furnished with bracteas. Very rarely it 
bears tendrils. 
6. Petiolus, the foot-stalk, fig. 13, is ap- 
plied exclusively to the stalk of a leaf, and 
is either simple, as in all simple leaves, or 
compound, as in the greater part of com- 
pound ones. Sometimes it bears tendrils. It 
is generally channelled on the upper side, 
and more or less dilated at the base ; in one 
or two instances the flower-stalk grows 
silt of it, as in turnera. Leaves that have 
no foot-stalk whatever are called sessile. 
The sap-vessels are for the most part very 
conspicuous in foot stalks, and their spiral 
coats are easily observed. 
6. Front, a frond. This term, which 
properly means a bough, is technically ap- 
plied by Linnaeus to express the stem, leaf, 
and fructification being united, that is, the 
leaf bears the flowers and fruit. The term 
is only used in the class Cryptogamia. 
Ferns which bear seeds on the back of their 
leaf are genuine instances of this, and it is 
applied to lichens, &c. Plate II. fig. 14. 
7 . Stipes, stipe, is the stem of a frond, fig. 
15, or the stalk of a fungus, as in the com- 
mon eatable mushroom. In the former in- 
stance it is very generally clothed with 
scales of a peculiar chaffy texture ; in the 
latter it is very often invested by a ring 
formed of the membrane which had previ- 
ously covered their fructification. 
OF THE LEAVES. 
The leaf, folium, fig. 16 and 17, is a very 
general organ of vegetables, yet not abso- 
lutely necessary to all plants, tor the stemx 
and stalks occasionally perform its functions. 
What those functions are we shall in a com- 
pendious manner explain. Leaves are gene- 
rally so formed as to present a large surface 
to the atmosphere; when they are of any 
o flier hue than green, they are said in botani- 
cal language to be coloured. Their duration 
is for the most part annual, but in some trees 
and shrubs they survive two or more sea- 
sons, and such plants being always in leaf 
are denominated evergreens. The internal 
surface of a leaf is highly vascular and pulpy, 
and is clothed with a cuticle very various in 
different plants, but its pores are always so 
constructed as to admit of the requisite 
evaporation or absorption of moisture, as 
well as to admit and give out air. Light 
also acts through this cuticle in a definite 
manner. That air and moisture and light 
have considerable, and even the most im- 
portant effects, upon the leaves of plants, 
has long been known to those who have stu- 
died the subject ; that heat and cold affect 
them is familiar to every one. The expe- 
riments of Hales, Bonnet, and others, have 
thrown much light upon the absorption and 
perspiration ofleaves, wuile those of Priest- 
ley and Ingenhouz have explained their ef- 
fects upon the atmosphere, and the manner 
in which air and light particularly act upon 
them. Leaves have a natural tendency to 
present their upper surface to the light, and 
turn that surface towards it in whatever di- 
rection it is presented to them. When 
