314 Dr. G. Ogilvie on the Vascular 



how unsatisfactory all the systems of classification are which 

 have been proposed in this order, these particulars may possi- 

 bly have a certain value, as increasing the store of facts bear- 

 ing on the general organography of the group, from which 

 it is to be hoped that some botanist may yet draw materials for 

 a more natural method of arrangement than any which has yet 

 been brought forward. The peculiarities, too, in these points, 

 are in some cases so striking that they appear worth recording 

 as specific characters *. 



A brown-coloured principle is very extensively distributed in 

 the organization of Ferns. It is particularly conspicuous in the 

 sporangia and other parts of fructification, and in the epidermis 

 of the stem, and the ramenta or scales with which it is clothed ; 

 and it is so characteristic of the group, that it communicates a 

 peculiar rusty tint to the vegetation of districts in which (as in 

 some parts of New Zealand) Ferns form a prevailing feature. 

 It is probably identical with the brown principle which occurs 

 in other foliaceous Cryptogamia, particularly in the stems and 

 capsules of Mosses ; and, whatever may be its chemical relations 

 — a point on which I can say nothing, — it at least resembles the 

 woody matter of phanerogamic plants in being deposited in the 

 interior of cells, in concentric pitted layers, on the inner aspect 

 of the first-formed wall of cellulose. The tissues in which it is 

 deposited often acquire great hardness, but are deficient in the 

 toughness of true wood ; on drying, especially, they become very 

 brittle. 



This brown matter is very constantly met with in the epider- 

 mic cells of the Fern-stem. The hardening of the cortical layer 

 in these plants, as in arborescent endogens, is even more neces- 

 sary for the support and defence of the stem than the accumu- 

 lation of the layers of bark in exogenous trees, on account of the 

 occasional deficiency of hard tissues in the interior of the rhi- 

 zome. Generally, however, there is a certain limited amount of 

 internal induration also ; for we find that particular tracts of the 



(see a criticism by Mr. Moore, Phytol., n. s., i. p. 378). There is a still 

 greater indefiniteness about the sectional views in Mr. Francis's ' Analysis 

 of the British Ferns.' Another reference given me by the same gentleman 

 (Duval Jouve, ' Etudes sur le Petiole des Fougeres,' in Billot's ' Archives 

 de la Flore de France,' pp. 50-149) I have been unable to verify, though I 

 have made inquiry for the work in the principal libraries in London. I 

 have not had access to the works either of Mohl or others of the German 

 botanists who have discussed the structure of Fern-stems, so that I cannot 

 say how far they may have gone over the same ground. 



* In this connexion I may refer to the great similarity in the disposition 

 of the dark tissue in the petioles of Scolopendrium vulgare and of Ceterach 

 qfficinarum (Grammitis Ceterach), once referred to the first-mentioned 

 genus. 



