THE METHOD OF CLIMBING OF LYGODIUM. 55 
make a substitute for a wire-wove mattress by no means to be 
despised. The leaf of an ordinary fern consists of a stalk and blade, 
the continuation of the former being called the midrib. The blade 
may be divided or undivided ; in the former case the divisions may 
be little leaves, each with its own stalk. In nearly all cases a 
leaf continues to increase in length for a certain time, when its 
growth is concluded. There is usually no further increase year after 
year. But the remarkable fern here being considered (Lygodiwm) 
is regulated by no such rule, for its midribs may continue to grow 
until the leaf is so long as to reach the tops of tall trees, thanks to 
its twining habit. The midrib has thus become a climbing-organ, 
and a leaf many yards in length is different altogether from what 
one imagines a leaf to be. At regular intervals lateral leaflets, which 
are also capable of great extension, are given off from the midrib, 
one at a time, and distant from each other about 4 inches, each 
being furnished with a very short stalk. As with the leaves of 
certain other ferns, so here two different kinds of leaflets may be 
noted—those which bear spores and those which function as ordi- 
nary leaves—but between the two are all kinds of transitional stages, 
interesting to observe. 
The term “ spore’ 
> 
needs some explanation. It is a single cell 
that becomes free from the parent plant and is capable of develop- 
ing into a new individual. The spores of ferns are contained in 
little bags (spore-cases), and groups of these make the dots or 
round patches on the under-surfaces of some of the leaves of ferns. 
Spores are frequently spoken of as “seeds,” but they are quite 
different, for no tiny plant ready for development is present in a 
spore, as there is in a seed. 
Those much-prized climbing-plants, the clematises, are tendril- 
climbers, the tendrils being modified leaf-stalks. The white clematis 
(Clematis indivisa) is the large white-flowered species (fig. 4); the 
small white clematis (C. hexasepala) has also white but smaller 
flowers; the yellow clematis (C. Colensot) produces masses of yellow 
flowers in the spring, and is especially abundant in Wellington and 
Taranaki.‘ The leafless clematis (C. afoliata)—not, however, a forest- 
plant—is a curious form which looks rather like a mass of rushes. 
It has few or no true leaves; but such would be a harm rather than 
a benefit, for the plant grows in extremely dry places, making dense 
bushes of entwining stems, which in the early spring are covered 
closely with their yellow flowers. All the New Zealand species of 
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