43^ 
VASCULAR CRYPTOGAMS. 
apparently extend over many years (see Braun, 'Rejuvenescence,' p. 123). Ac- 
cording to Mettenius, the lamina of some Hymenophyllaceae is capable of unlimited 
development, and is annually renewed. In Lygodium the primary branches of the 
lamina remain also in a bud-like condition at the end after the formation of each 
pair of pinnae of the second order, while the rachis of the leaf grows without 
limit and resembles a twining stem. 
Fig. -io-i.—Aspidrnm Fih'x-mas; A longitudinal section throug-h tne end of a stem, v the apical part of the stem st, 
b b leaf-stalks, b' a young leaf still rolled up, the rest enveloped in long hairs, fibro-vascular bundles ; B a leaf-stalk of 
the same plant broken off, bearing at k a bud with several leaves, 70 a root of this bud ; C a similar leaf-stalk cut through 
lengthways, bearing a root at w and a bud at /t ; D end of a stem with the leaf-stalks cut off with the exception of the 
youngest leaves of the terminal bud, in order to show the arrangement of the leaves, the spaces between the stalks b b 
are filled with numerous roots which themselves all spring out of the stalks; E end of a stem the cortex of which has 
been peeled off in order to show the net-work of fibro-vascular bundles^; Fa mesh of this net-work slightly magnified, 
showing the basal portions of the bundles which pass into the leaves. 
The branching of the lamina of Fern-leaves is not unfrequently forked in the 
mature state, as in Plaiy cerium, Schizcea, &c. ; but Hofmeister refers also the pinnate 
forms to dichotomous branching at the commencement, which becomes sympodial 
with further development, a right and left limb of the bifurcation being alternately 
weaker in its growth, and forming the lateral pinnse ; while the branches, the growth 
of which is favoured, form the rachis of the leaf or of the branch of a leaf ^. 
^ It must be observed here also that Hofmeister applies the term 'dichotomy ' in a much wider 
sense than is usually done. New examinations of a large number of species are greatly to be desired. 
