PROTOPHVTA^ 
CLASS L 
PROTOPHYTA. 
In this class are coraprised the most simple and minute of all plants, whether 
they contain chlorophyll, and therefore have been regarded as belonging to the 
Algae, or whether they contain no chlorophyll, as the Yeast-fungi and the so-called 
Schizomycetes (Bacteria, etc.). 
Those Protophytes which contain chlorophyll live chiefly in water, or at least 
in damp localities, sometimes as pseudo-parasites, and their green colouring matter is 
often mixed with a blue one which is soluble i^i water. Those which are 
destitute of chlorophyll are either true parasites or inhabit the moist surfaces of 
organic bodies, or are found in fluids which contain organic substances in solution 
from which they derive their nutriment, and which they decompose, causing 
putrefaction or fermentation. 
The structure of Protophytes is always extremely simple, and in the 
simplest of all the cells are so small that they can be seen only under a high 
magnifying power. In the smallest a distinction can scarcely be detected be- 
tween cell-wall and cell-contents; and when this can be done the contents are 
homogeneous, or minutely granular. The cell-wall has a tendency to deliquesce 
into a soft jelly in which the cells remain imbedded either regularly or irregularly; 
but sometimes it only swells up, and is then manifestly stratified. 
In the simplest forms the cells are isolated ; the two halves of a divided mother- 
cell increase till they attain its size, and then again divide; the derivative cells 
separate, and carry on an independent life. In the more highly developed forms 
the derivative cells remain united, and the final result is either simple and often 
extremely slender rows of cells, thin lamellae, cell-division taking place in one plane, 
or agglomerations in consequence of cell-division taking place in all directions. 
It is only in the most perfectly developed individual that the multicellular body 
has a determinate external form. 
The species which contain chlorophyll are in general larger than those which 
do not, and the structure of their cells more perfect ; the largest and most perfectly 
developed among the latter being Yeast-cells. Even in this, the lowest stage in the 
vegetable kingdom, the want of chlorophyll is seen to be usually associated with 
a degradation of structure. All the cells in the individual are usually exactly 
alike ; it is only in the higher forms that a few larger cells of a different colour 
— termed Heterocysis — are intercalated among the otherwise similar cells of a 
filament. 
In most cases there is no distinct base and apex, and therefore no definite 
direction of growth; but in a few of the highest members of the class a base 
