84 
FERNS, AND THEIR MANAGEMENT. 
physiologists, followed by a few observations that have resulted from practical inves- 
tigation and comparison of facts. 
To furnish, then, a condensed idea of the structure of any leaf, we take, as a 
first position, the following from p. 196 of Lindley's Elements. 
" A leaf consists of a petiole^ or stalk ; a lamina^ or blade ; and a pair of 
stipules " — ^. e. (a diminutive of stipes)^ props, adjuncts, or more properly, accessary 
appendages, which, though common, are by no means necessary accompaniments 
of a perfect leaf. The petiole has been already considered. 
2. The lamina or plate is described as "an expansion of the parenchyma of the 
petiole, and is traversed by veins, which are ramifications or extensions of the 
bundles of vascular tissue of the stalk ; or, when that is absent, of the stem." 
We find no defect in this position, other than that it sanctions the idea of an 
expansion of cellular tissue in the lamina. Now, a leaf^ however minute it may 
be in the bud, is equally formed in all its parts, the lamina existing coincidentally 
with its stalk ; and it is admitted {idem. No. 184) that " leaf-buds originate 
universally in the horizontal or cellular system." Then all the parts of buds, of 
which leaves form one of the most important, have been developed perfect in their 
miniature proportions from the first moment of their existence. If this be correct, 
the tissue or cellular membrane of the full-grown lamina is an expansion, or 
growth of parts already existing, not a mere elongation of an exterior member. 
But all leaves, according to modern physiology, are not necessarily supplied with 
laminge ; for it supposes (as in many Acacias) that the petiole itself is leafy (?), the 
true lamina being abortive ; and then this pseudo-leaf is called Phyllodium. 
3. The veins are two-fold ; one stratum belongs to the upper, the other to the 
under surface. " The upper conveys the juices from the stem into the lamina, for 
the purpose of being aerated and elaborated ; the under returns them into the bark." 
This arrangement is extremely interesting ; and it may be investigated by the 
careful anatomy of a leaf whose cellular tissue has been broken up, as we find it 
in decayed leaves. This double ramification implies a two-fold office, and seems 
to point to an analogy with the venous and arterial systems of animal structure. 
However this may be, and whether or not there exists an anastomosing process 
between the two systems, the importance of the foliage is thereby enhanced, and 
rendered still more evident. 
FEUNS, AND THEIR MANAGEMENT. 
To an unrefined mind, no plants would appear to be ornamental but those 
which bear showy flowers. Conspicuous colours seem essential to the production 
of what an ordinary taste would account beautiful in vegetation. And thus, the 
whole race of Ferns, with all their elegance and attractiveness, would be banished 
as unworthy of cultivation. 
