5i6 
Tans ley and Lulham.—A Study of the 
In Anemia coriacea 1 there is a continuous sclerenchymatous pith not in 
connexion with the endodermal pockets. This Boodle also interprets as 
a reduction-phenomenon, and the same applies to Platyzoma , where the 
pith has no connexion either with cortex or leaf-trace. But in the young 
Matonia there can be no reason to postulate reduction, and the evidence 
cited is, we think, sufficient to show that the pith of the stem does not 
necessarily arise in connexion with cortex 1 2 . 
Boodle has made a suggestion with regard to the teleological cause of 
the origin of pith in Ferns. ‘ To admit of the insertion of a number of large 
arched bundles, the stele increased its diameter beyond the size required 
by the exigencies of water-conduction, and the central part of the xylem 
of the stele was transformed into parenchyma or other tissues 3 / This 
seems to us an extremely probable view, though we should be inclined 
to regard the Lindsay a- type as normally antecedent to the production 
of a parenchymatous pith 4 . But in certain cases at least the pith may 
well have had a specific function of its own from the outset. In species with 
superficial creeping rhizomes and large leaves on long erect petioles, the tissues 
of the rhizome on which the base of the petiole is inserted must be subject 
to a considerable strain, which might lead to rupture of the vascular system 
at the junction of leaf-trace and stele. This danger would certainly be 
lessened by the insertion of a T-piece of hard material, the stalk of which 
occupies the centre of the leaf-trace and the cross-piece that of the stele. 
This T-piece is represented by the strand of sclerenchyma in the concavity 
of the trace and the sclerenchymatous pith of the stele to which it is 
attached, as actually found in many Ferns. Additional solidity would be 
acquired by the connexion of the T-piece with the thick- walled cortex of 
the stem and base of the petiole, and this condition is actually realized in 
most cases, where the leaf-trace is open at the base, but it is not essential to 
the mechanical efficiency of the arrangement which appears to obtain in 
the young Matonia . In some cases the strand of sclerenchyma in the 
concavity of the trace is continuous with a sclerized pith in one (the 
basipetal) direction only (. Davallia pinnatd). A study of various living 
Ferns in their natural habitat is required to confirm or disprove this idea. 
If the view taken above, that the pith is to be regarded as a new tissue 
of the stem, is just, it follows that the same considerations must hold of the 
internal accessory vascular cylinders of Matonia and equally of other poly- 
1 Boodle (’01), p. 387. 
2 Cf. also Gleichenia dichotoma. Gwynne-Vaughan (’03), p. 739? has set out the alternative 
methods of evolution of a pith in Ferns. 
3 Boodle (’03), p. 530. 
* Partly because of the large number of cases now known (see p. 509, supra) in which the Lindsaya- 
type precedes solenostely in ontogeny, and partly because, as Gwynne-Vaughan (’03) has shown, 
the type of leaf-trace associated with the Lindsay a - stele is still compact and would not require a 
wide medulla ted type of stele for its attachment. 
