317 
MOT 
or ftones, though it likewise makes ufe of them in its pro¬ 
greflive motion. By means of thefe horns and prickles, 
it is enabled to walk either on its back or its belly; but 
it mod commonly makes ufe of thofe which are near the 
mouth. Occafionally it has a progreflive motion by turn¬ 
ing round like a wheel. See the article Echinus, vol. vi. 
p. 217. 
The animals called fen-nettles, or Mednfee , though ex¬ 
tremely flow in their motions, are neverthelefs evidently 
capable of moving at pleafure from place to place. The 
variety of their form is fuch, that it is difficult to aflign 
them any determinate figure whatever. In general, how¬ 
ever, they refemble a truncated cone, the bafe of which is 
applied to the rock to which they adhere. Their colpurs 
are various, whitifh, brown, red, or greer.ifh : the mouth 
is very large ; and when opened appears furrounded with 
filaments refembling the horns of lhails, which, being dif- 
pofed in three rows around it, give the animal the ap¬ 
pearance of a flower; and through every one of thefe the 
animal has the power of fquirting the fea-water. The 
ftrufture of thefe animals is extremely Angular ; they con¬ 
fiding all of one organ, viz. a flomach. When fearching 
for food, they extend their filaments, and quickly entan¬ 
gle any fmall animals that come within their reach. The 
prey is inftantly fwallowed, and the mouth flint clofe upon 
it like a purfe; in which date it remains for many days 
before the nutritive parts are extrafted. The animal, 
though fcarcely an inch or an inch and a half in diameter, 
is neverthelefs fo dilatable, that it can fw'allow large whelks 
and mufcles, the fhells of w hich are thrown out by the 
mouth after the nutritive parts have been exhauded. 
Sometimes the fliell is too large to be voided this way; in 
which cafe the body of the animal fplits, and the fliell is 
voided through the opening, which in a lliort time heals 
up again. The progreflive motion of this creature is fo 
flow, that it refembles that of the hour-hand of a clock, 
and is performed by means of innumerable mufcles placed 
on the outlide of the body. All thefe are tubular, and 
filled with a fluid, which makes them projeft like prickles. 
On occafion it can likewife loofen the bafe of the cone from 
the rock, and, inverting its body, move by means of the 
filaments already mentioned, which furround the mouth ; 
but even the motion performed in this manner is almod 
as flow as the other. See the article Medusa, vol. xv. 
Vegetable Motion. Though vegetables have not the 
power of moving from one place to another like animals, 
they are neverthelefs capable of moving their different 
parts in fuch a manneras would lead us to fufpeft that they 
are aftuated by a fort of inftinft. Hence many have been 
induced to fuppofe, that the animal and vegetable king¬ 
doms are in a manner indiftinguilhable from one another ; 
and that the higheft "degree of vegetable life can hardly 
be known from the lowed degree of animal life. The ef- 
fential and infuperable diftinftion, however, between the 
two, is the faculty of fenfation, and loco-motion in confe- 
qucnce of it. Were it not, indeed, for the manifeftation 
of fenle by moving from one place to another, we fhould 
not be able to tell whether vegetables were poflefled of 
fenfation or not; but, whatever motions they may be 
poflefled of, it is certain that no vegetable has the faculty 
of moving from one place to another. The roots of a tree 
indeed will change their direftion when they meet with 
a ftone, and will turn from barren into fertile ground ; 
but this is evidently mere mechanifm, without any proof 
of will cr fenfation ; for the nourifliment of the root comes 
not from the ftone, but from the earth around it; and the 
increafe in fize is not owing to any expanfion of the matter 
which the root already contains, but to the appofition of 
new matter; whence the increafe of fize mult always take 
place in the direftion from whence the nourifliment pro¬ 
ceeds. On this principle alfo may we explain the reafon 
why the roots of a tree, after having arrived at the edge of 
a ditch, inftead of fliooting out into the air, will creep 
down the one fide, along the bottom, and up the other. 
In their other movements the vegetables difcover no- 
Vol. XVI. No. ic 9 7— 
I O N. 
thing like fenfation or defign. They will indeed uni¬ 
formly bend towards light, or towards water; but in the 
one cafe we muff: attribute the phenomenon to the action 
of the elements of light and air upon them; and, in the 
latter, the property feems to be the fame with what in 
other cafes we call attraction. Thus, if a root be unco¬ 
vered, and a wet fponge placed near it in a direction dif¬ 
ferent from that in which the root was proceeding, it will 
foon alter its pofition, and turn towards the fponge; and 
thus we may vary the direftion of the root as often as we 
pleafe. The efforts of a plant to turn from darknefs or 
fliade into funfliine are very remarkable ; as, in order to 
accomplifli this, not only the leaves will be inclined, but. 
even the ftems and branches twilled. When a wet fponge 
is held under the leaves of a tree, they bend down in order 
to touch it. If a veflel of water be put within fix inches 
of a growing cucumber, in lefs than twenty-four hours 
the latter will alter its direftion ; the branches will bend 
towards the water, and never alter their courfe until they 
come in contaft with it. The moll remarkable inllance 
of this kind of motion, however, is, that, when a pole is 
brought near a vine, the latter will turn towards it, and 
never ceafe extending its branches till it lays hold of the 
fupport. 
The motions of the fenfitive plant, and others of the 
fame kind, have been confidered as very wonderful; but 
it is doubtful if any of them be really more fo than that 
of the vine juft mentioned. None of thefe lliow any kind 
of propenlity to move without an aftual touch. A very 
flight one, indeed, makes the fenfitive plant contract, and 
the whole branch, together with the leaves, bend down 
towards the earth. Thefe phenomena are by 1 ’ome af- 
cribed to eleftricity. (See Mimosa.) Even the motions 
of the Hedyfarum gyrans, which at firft fight feems fo 
much more furprifing than thofe of the fenfitive plant, 
may it is fuppofed admit of explanation upon the fame 
principle. The American plant called Diontea mufcipula, 
or Venus’s fly-trap, is another example of very wonder¬ 
ful mechanifm in vegetables, though even this does not 
argue any degree of fenfation in this plant more than in 
others. The leaves of the Dionsea are jointed, and fur- 
nilhed with two rows of prickles. A number of fmall 
glands upon the furface fecrete a fvveet juice, which en¬ 
tices files to come and fettle upon it; but the moment 
thefe infefts touch the fatal fpot, the leaves fold up, and - 
fqueeze them to death between the prickles. The leaves 
fold up in the fame manner when the plant is touched 
with a ftraw or pin. The Drofera rotundifolia and lon- 
gifolia, round and long-leafed l’undew, plants of our own 
country, not uncommon in boggy ground, poflefs a fimi- 
lar ftrufture, and perform limilar functions. 
The folding up of the leaves of certain plants in the 
abfence of the fun’s light, called their Jleep, affords another 
very curious inftance of vegetable motion. Almoft all 
vegetables, indeed, undergo fuch a remarkable change 
in the night, that it is difficult to know exactly how many 
kinds do really fleep. They fold up their leaves in many 
different ways; but all agree in difpofing of them in fuch 
a manner as to afford the bell protection to the young 
ftems, flower-buds, or fruit. The leaves of the tamarind- 
tree contraCl round the young fruit in order to p rot eft it 
from nofturnal cold ; and thofe of fenna, glycina, arid 
many other papilionaceous plants, difpofe of their leaves 
in the fame manner. The leaves of the chickweed, afcle- 
pias atriplex, &c. are difpofed in oppofite pairs. In the 
night time they rife perpendicularly, and join fo clofe at 
the top, that the flowers are concealed by them. In like 
manner do the leaves proteft’ the flowers of the Sida or 
Althaea theophrafti, CEnothera, Solanum, and the Egyp¬ 
tian vetch. All thefe are ereftecl during the niglit; but 
thofe of the white lupine, in time of lleep, hang down. 
The flowers of plants alfo have motions peculiar to 
themfelves. Many of them during the night are enclofed 
in their calyxes. Some, particularly thofe of the German 
fpurge, Geranium ftriatum, and common whitlow-grafs, 
H h when 
