CLASSIFICATION 7 
The third group, that of the ferns, comes very near 
to the ordinary plants we know so well, for the vessels 
and fibres are now well developed. They have obtained 
their skeleton, they have fully-equipped roots and leaves, 
but they have not yet reached the stage of producing 
seeds, which are complete plants in miniature. 
Now we reach the fourth group, that of the flowering 
plants. All of these have flowers, generally fairly con- 
spicuous, and they produce seeds which enclose within 
them rudimentary stem, roots, and leaves. 
In one or other of these four great groups are arranged 
every one of the plants, and though occasionally one or 
two individuals may seem to belong half to one and 
half to the other, their general distinctions are plain 
-enough, 
These classes, however, are still too large for con- 
venient working, and must be further broken up. In 
Class I. we have already separated seaweeds and 
funguses. For the present it is sufficient to note that 
the first are always coloured with chlorophyll, a sub- 
stance we shall see more of later; the second never. 
In the moss class we may separate the liverworts 
(Chap. VIII.) from the mosses proper, and in the ferns 
. (Chap. IX.) the horsetails from the ferns proper. 
When we come to the flowering group, we make a 
great division, according to the way in which the seed 
is kept ready for fertilisation. Among the pines and 
firs (Chap. XI.) the seed lies open and exposed, but 
the rest of the flowering plants have developed one 
step further, and guard it in some kind or other of 
~ seed-vessel. 
This still leaves us with an unmanageable number of 
plants with a closed seed-vessel, and they are further 
