78 TYPES OF BRITISH PLANTS 
again and again just the same arrangements of cells. 
Not such are the great tree-ferns, with trunk and roots, 
and a crown of spreading fronds that rivals those of 
the palm trees. In them we find true complexity, and 
a steady development to higher things. 
The mosses, as we saw, had stem and leaves, but we 
were as yet among the strictly cellular plants, and the 
vessels were only foreshadowed by the occasional appear- 
ance of a line of cells uniformly altered in the thickness, 
or shape, of their walls. Now we have true fibro-vaseular 
bundles, and we can trace their ramifications upon the 
fern’s veined leaves. Like those of the monocotyledons, 
they are generally “closed” (p. 20); that is, they have 
no cambium ring, making for continued growth and 
development, but they have learned the secret of com- 
bining cells into vessels, and thereby of securing freer 
and more rapid transport from part to part of the 
materials necessary for a prosperous life. 
And here I must make a digression. When I have 
used these phrases about plants “learning” or “ trying” 
to do something, I have not meant to imply any theory 
of plant intelligence. The phrase has been used simply 
as a convenient expression for the fact of the develop- 
tnent of new features. 
Whether each plant was inspired with unknown 
instincts, always aiming towards higher developments, 
or whether these changes to higher forms are simply 
the result of the survival of the best-equipped for the 
battle of life is far too wide a problem to be discussed 
here. For the present, we may be well contented if we 
can obtain some general outline of the main facts of 
the plant world as they now stand. It is only after 
accumulation of knowledge, not only upon the main 
