88 FIRST FORMS OF VEGETATION. 
seen to harmonize the most dissimilar works of 
nature, as if to show that they proceeded from 
the same creating Hand. There may bea gradual 
transition from one class of plants to another, and 
certain characters may be common to _ two 
families; but still there are definite groups in 
nature, and typical characters belonging to 
plants, which will for ever keep them distinct and 
isolated, as illustrations of the infinite variety of 
the Divine works. 
The first pages of the earth’s history reveal 
to us very extraordinary facts with relation to 
members and allies of the moss tribe. The club- 
mosses, in particular, at a former period, seem to 
have played a more important part, or to have 
found conditions more suitable to their luxuriant 
development than is the case at the present day. 
The two or three hundred species at present 
existing are the mere remnant of a once magnifi- 
cent group. Some of them are stated to have 
formed lofty trees eighty feet high, with a propor- 
tionate diameter of trunk. They are among the 
most ancient of all plants. The oldest land-plant 
yet known is supposed to be a species of lycopo- 
dium closely resembling the common species of our 
moors. In the upper beds of the Upper Silurian 
rocks, they are almost the only terrestrial plants 
yet found. In the lower Old Red Sandstone they 
