188 CHLOROSPERME^:. 



phase ; and at the other side vegetable life, in an equally low 

 condition. Some such boundary seems to sever such animals 

 as the- sponges, from such vegetables as the less perfect 

 chlorospermatous Algae but our present knowledge of 

 either tribe is insufficient to permit us clearly to define in 

 words what the exact limits of this bounding line may be. 

 In such a case it is much safer to leave the point undeter- 

 mined, seeing that the probabilities are greatly in favour 

 of the belief that, could we know the matter perfectly, such 

 a boundary line would be discovered. 



The least organized of the Chlorosperms consist of a single 

 cell, containing a granular matter called endochrome, identi- 

 cal with that found in the cells of the higher vegetables. 

 These very simple plants usually multiply by spontaneous 

 fissure, the internal mass separating into two or more parts, 

 round which a membrane is formed, and which thus be- 

 come cells developed within the walls of the original cell. 

 These cells burst through the mother-cell and become dis- 

 tinct plants, propagating others at maturity in a similar way. 

 Such is the method of increase in the Protococcus or Red- 

 snow plant, whose sudden appearance is readily accounted 

 for by this process of multiplication, by which, in a very few 

 generations some millions of individuals will result from one 

 original cell. If the plant have existed on the surface of the 

 soil on which the snow- falls, its progress upwards through 

 the snow, as new individuals are produced, will be very ra- 

 pid, and thus vast spaces, many feet in thickness, are 

 frequently tinged by a plant of extreme minuteness so 

 small, that except when seen in masses, it is scarcely appre- 

 ciable by the eye. Sir John Ross encountered it in Baffin's 

 Bay, covering tracts of miles in extent, and often penetrating 

 to the depth of ten or twelve feet. 



Other simple Chlorosperms are propagated by the conjuga- 

 tion of two cells. This is the case in the Diatomaceae and 

 DesmidiaceoB and in many of the Confervoid tribes. In the 

 case of the simpler Desmidiacete, where the frond consists of 

 a single cell, two fronds come together a passage is formed 

 from one to the other, and in the intermediate space the 

 whole contents of both the parent-cells are poured, resulting 

 in the fructification or spore. The history of such plants 

 is analogous to that of annuals, which die when they 

 have perfected their seeds. But besides this mode of 

 propagation, they are likewise multiplied by the vivifi- 

 cation and growth of the green matter with which they are 



