FRESH-WATER ALG&. 239 
have been. Their fundamental structure, in 
almost all cases, appears to be simply a mass 
of cells variously arranged in a jelly-like poly- 
morphous substance, to which the name of frond 
has been applied, more for the sake of con- 
venience than from any sense of its propriety ; 
each cell being a distinct individual plant, ap- 
parently having no connexion with the other cells 
to which it is placed in juxtaposition, and per- 
forming for and by itself all the processes of 
nutrition and reproduction. The question natur- 
ally arises, whether these obscure and extremely 
simple organisms which stand at the very lowest 
extremity of the vegetable kingdom, be really 
perfect plants, or rather the commencement, the 
first of the transitional stages of more highly 
organized plants, unable to develop themselves 
owing to their being placed in unfavourable 
circumstances? Some eminent botanists have 
contended that the spore germs of the lower 
cryptogamic plants are in all cases precisely the 
same, developing themselves into different plants 
according to the medium and the circumstances 
in which they are placed: becoming palmellas 
when produced on moist rocks, conferve in 
streams, confervoid mosses on shady banks and 
fields, lichens on dry rocks when stimulated by 
the action of light, and fungi when produced on 
