INTRODUCTION. 5 
slimy matter forming a scum on the surface, or 
floating in long filaments in the depths. On 
almost every fallen leaf and decayed branch, fleshy 
gelatinous bodies of different forms and sizes meet 
our eye. Sometimes all these different objects 
appear growing on the same substance. If we 
examine a fallen, partially decayed twig, half- 
buried in the earth in a wood, we may find it com- 
pletely covered with various representatives of 
these different vegetable growths; and nothing 
surely can give us a more striking proof of the 
universal diffusion of life. All these different 
plants belong to the second great division of the 
vegetable kingdom, to which the name of crypto- 
gamia has been given, on account of the absence, 
in all the members, of those prominent floral 
organs which are essential to the production of 
perfect seed. They are propagated by little embryo 
plants called spores or sporules, generally invisible 
to the naked eye, and differing from true seeds in 
germinating from any part of their surface instead 
of from two invariable points. Besides this grand 
distinguishing mark, these plants possess several 
other peculiar qualities in common. They consist 
of cells only, and hence are often called cellular 
plants, in contradistinction to those plants which 
are possessed of fibres and woody tissue. Their 
development is also superficial, growth taking 
