338 
POPULAE SCIENCE EEVIEW. 
metliod can we attain the end in view ? Indeed, from the 
facts shown of late years, it is clear that till this is done we 
must consider many of the simpler forms, at least, as only 
provisionally placed in the present scale of vegetable life. 
Having premised thus much, let me point out some instances 
of the similarity between the so-called Palmellacese and the 
cells produced by lichens, mosses, &c. 
If we place under the microscope a small portion of the 
green grains found on the bark of every tree, paling, or wall in 
winter, it will be seen to resemble the cells in fig. 1, 
Plate XIY. To it has been given the name chlorococcus,^^ 
or green berry. This growth is very easily obtained and 
observed. It consists in the full-gpown state of a single cell 
(fig. 1, a), with green contents, and a nucleus in the centre. 
The contents are not entirely uniform, but somewhat granular 
and slightly radiating from the central nucleus. But all are 
not single cells. Some are divided by a line in two portions, 
and subdivided into two cells, which form is called binary 
segmentation (fig. 1, h). Some are divided crosswise by two 
partitions into four parts, the plan being called quaternary 
segmentation (fig. 1, c). These processes form a common mode 
of multiplication. Division may proceed with such vigour 
that it extends to the fourth or fifth generation before 
it is complete in the first. Sometimes, as before stated, it 
passes on to the reduction of the cell to exceedingly minute 
portions, which, endued with the power of growth, gradually 
increase in size without dividing, and at last resemble the 
parent cell. Again, division may take place in a radiating 
manner, so that five or six wedge-shaped portions may be pro- 
duced, which will, when separated, become round cells. Some 
of the smaller divisions, instead of dividing as usual, elongate 
first in one direction, and then divide into two parts across 
the middle without separation ; by this process, continued 
growth and division thus proceeding simultaneously, a long 
jointed filament is produced, which by a retroversion of the 
process may ultimately reproduce the round cell. 
The reader has been detained over this somewhat tedious 
description in order to make him acquainted with the ordinary 
process of division of single cells, whatever their origin. 
Let us now see how this chlorococcus may be imitated. 
If any one will allow snow to fall thickly on a clean sheet of 
glass, and pour it, when melted, into a deep glass, he will 
observe some dark matter setthng to the bottom. When this 
is placed under the microscope, amongst others, forms similar 
to those of chlorococcus will be found. Attached to some of 
them he will observe some transparent colourless fibres, in 
some cases holding some of the cells together. To one accus- 
