_ A BOTANICAL EXCURSION IN MY OFFICE. 529 
utricle grows inwards, and, dividing the protoplasm and 
contents more and more completely, finally meets in the 
centre, and the single cell has been divided into two, 
each half of the original size. ‘These small cells now in- 
crease in size by an interstitial growth of their cell-wall 
until they reach their full size, when, perchance, the pro- 
cess recommences. Sometimes a globular cell will divide 
into three, four, or more parts, but the process is essen- 
tially the same. In Sree cell formation, the protoplasm of 
a cell condenses into a varying number of little masses, 
which, whilst lying free in the interior of the mother cell, 
Secrete, each around itself, a cellulose wall. In this way 
is formed a number of perfect cells, en- Fig. 6. 
closed in, but independent of, the original 
cell, by whose dissolution they are finally ahi 
Set free. 
But let us return to our little plant and 
observe together a cell about to divide. 
The first noticeable change is the appear- . 
ance of a dark streak around the cell near i 
the distal end. At the position of this Two cells taken from 
. a species of (£do- 
streak outgrowths take place from the gonium growing in 
primordial utricle as just described, and cpm coed the 
divide the old cell into two parts, the up- in which division is 
per being much the smaller. (Fig. 6.) p AE gh enin vean 
Watching the dark streak just spoken of, Ue senile oF oid 
in a little while it begins to widen into a Giochrome;’ a its 
trench, and still continues to widen; the lose wall: d, old cel 
upper smaller division is growing by an separated 
elongation of the primordial utricle at the line of separa- 
tion of the two parts. As the primordial utricle grows, 
it bears the old cellulose wall, like a cap upon its end; 
and, when it secretes its own proper cellulose wall, the 
AMERICAN NAT., VOL. I. 67 
