43* 



VASCULAR CRYPTOGAMS. 



apparently extend over many years (see 13raun, '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. ■yyz.—Aspidium Filix-mas ; A longitudinal section through the 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, i^ fibro-vascular bundles ; B a leaf-stalk of 

 the same plant broken off, bearing at /(; a bud with several leaves, w a root of this bud ; C a similar leaf-stalk cut through 

 lengthways, bearing a root at lu and a bud at h; 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 g; F a 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 Platycerium, 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. 



