ALGJE. 141 



for them ; now these are the corn-bearing plants, the most 

 useful to the animal world, and upon which it in reality 

 depends for existence. Moreover the whole of the mould 

 in which the higher orders of plants grow, is formed by the 

 decomposition of the more humble grades, especially the 

 lichens, which first take possession of the surface of bare 

 rocks and stones, and furnish by their death food fit 

 for the sustenance of those which follow them. Like the 

 higher orders of vegetation, these minute plants excrete 

 oxygen, and thus in the ocean may supply this vital element 

 for the respiration of the various corresponding minute 

 animal organisms which inhabit the depths of the sea and 

 which cannot come to the surface to get it, so that the two 

 thus supporting each other, form food for all the higher 

 marine animals, which are finally eaten by man. So that 

 upon some of these minute and apparently useless creatures 

 hang the lives and well-being of many of the most important 

 vegetables and animals. 



Dr. Lindley divides the acrogens into the following 

 orders : 



1. ALG^: (Algals), including Sea-weeds, &c. 



The Algae include the lowest of all the vegetative 

 organisms, the " Protophytes " (first plants). These 

 have no individual parts, but consist of living cells, 

 propagating by sub-division or by the union of two 

 cells into one, causing the formation of " nuclei " or 

 smaller cells within them, each of which becomes a 

 parent cell after the rupture of the cell-membrane 

 which contained them. 



Dr. Carpenter, in his " History of the Microscope," 

 says : " The life-history of one of these uni-cellular 

 plants in its most simple form, can scarcely be better 

 exemplified than in the Palmoglcea macrococca, one of 

 those humble forms of vegetation which spreads itself 

 as a green slime" over damp stones, walls, &c. When 

 this slime is examined with the microscope, it is found 

 to consist of a multitude of green cells, each surrounded 

 by a gelatinous envelope ; the cell, which does not seem 



