Chara, which are all branched, consist of elongated cells
placed end to end, and tapering in size from below upwards
; surrounding these primary cells there are, in the perfect
state of the plant, a number, in Chara vulgaris usually
eighteen, of smaller secondary cells: these take a spiral course
round the larger cell invariably from left to right. From
the upper extremity of each cell grow out nine arms or
smaller cells arranged In a campanulate manner; each of
these arms have four or five joints, from which issue the
organs of reproduction, to be described hereafter. From the
superior extremity of many of the cells also grow out branches,
and at the same time long and colourless branched articulated
roots are sent forth. The genus Nitella differs only from
Chara in the absence of the secondary spiral cells, and in.
the number of arms Avhich go to form each verticillum or
whorl.
The circulation in Chara was first noticed by Amic i; in
the two genera it does not differ materially, in both the course
is spiral; the fluid, with its granules, passing obliquely and
slowly from left to right up one side of the cell, turning
round its extremity and descending in the same manner on the
other side. A circulation of the same character prevails not
only in the main cells of the stems and branches, but also in the
secondary spiral cells or tubes, some of Avhich are occasionally
articulated or divided into other small cells, each, in like
manner, having an independent circulation.
Mr. Slack (Transactions Soc. of Arts, &c., vol. xlix. p. 1.)
long since observed, and the observation has been verified,
tha t the ascending current of the circulating fluid is ahvays
in that half of each cell which is farthest from the axis of
the p la n t; the descending, as a consequence, being confined
to the opposite half, or tha t which is nearest the axis. The
same observation Mr. Varley states to hold good in respect
to the roots, due allowance being made for the difference in
their direction, they, unlike the plant itself, taking a downward
course.
A deviation from the above-described circulation has been
noticed to occur in certain parts of Chara vulgaris by Mr.
Solly, and has been described by Mr. Varley in one of his
excellent memoirs on Chara in the “ Transactions of the Soc. of
Arts,” vol. xlix. p. ii. This deviation occurs in many of the
cells which usually surround the seeds, and which are four
in number when complete. I t occurs, see plate Lxi. fig. 1.
of the present Avork, in those cells or sprouts surrounding the
seeds marked a, b, c, d, e , f , g, h, in Avhich the sap has taken
a circular or cylindrical course round the axis. Mr. Varley
thus minutely describes this deviation.
“ F ig. 2. (pi. LXI.) is an enlarged view o f the sprout a. The
circulation is over to the right, as shown by arrows; it thus
far agrees Avith the spiral course, Avhich is always to the right.
Near the point by the top arroAV, there is such an accumulation
as to form a ring or thick mass very like a diaphragm ;
this mass keeps revolving on its own axis. Near the second
and third arroAVS the particles are more detached, each going
round in its own circ le; here the green studs, instead of being
arranged in a straight line, are slightly curved. Still lower
down, near the middle of the sprout, there is an inclined
elliptical circulation, shoAvn by dots and arrows; and from the
bottom, particles are seen rising nearly as high as the oval,
and descending again without appearing to follow any regular
course: these are shown by dots and arrows.
“ Some of the particles in sprout (a) were of sufficient
size to be distinctly seen during the Avhole of their revolution,
which took place in about fourteen or fifteen seconds: this
observation was repeated by different persons, who nearly all
agreed as to the time of the revolution; but in one of the
sprouts I observed three particles differing in their speed,
and occasionally passing each other. I counted their periods
hy my own pulse ; one went round in nine beats, the next in
e le v en ; these followed so nearly in the same track as to
move aside Avhllst passing; the third sometimes occupied
tAventy beats, and at other times twenty-five in going round.
They all appeared to keep to the circumference, and therefore
the difference in their periods is more AA^orthy of being remarked,
as seeming to indicate that each particle had some
cause of motion independent of the fluid in Avhlch it moved.”