PROTOPHYTA, ^45 



CLASS I. 



PROTOPHYTA. 



In this class are comprised 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.). 



i Those Protophytes which contain chlorophyll live chiefly in water, or at least 

 1 damp localities, sometimes as pseudo-parasites, and their green colouring matter is 

 ften mixed with a blue one which is soluble in water. Those which are 

 estitute of chlorophyll are either true parasites or inhabit the moist surfaces of 

 rganic bodies, or are found in fluids which contain organic substances in solution 

 ■cm 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, 

 is only in the most perfectly developed individual that the multicellular body 

 ,s a determinate external form. 



The species which contain chlorophyll are in general larger than those which 

 not, and the structure of their cells more perfect ; the largest and most perfectly 

 veloped among the latter being Yeast-cells. Even in this, the lowest stage in the 

 igetable kingdom, the want of chlorophyll is seen to be usually associated with 

 degradation of structure. All the cells in the individual are usually exactly 

 ke; it is only in the higher forms that a few larger cells of a diff'erent colour 

 ;ermed Heterocysts — are intercalated among the otherwise similar cells of a 

 ,ment. 



In most cases there is no distinct base and apex, and therefore no definite 

 ection of growth; but in a few of the highest members of the class a base 



