290 



PRIMA RV ARRANGEMENT OF TISSUES. 



The inmost of these zones diflcrs in individual cases: in some, investigated by Mette- 

 nius, it is composed of two flat small bundles, which appear curved in transverse section ; 

 in others, on which Karsten's statements appear to be based, there is a solid cylindrical 

 bundle. Karsten says of this that it ends freely in the pith below: this does not coincide 

 with the data given above, chiefly after Mettenius, and requires further examination. 

 Of the Marattiaceai with several rings of bundles as seen in transverse section, the 



cylindrical stem of the species of Danaea with on 

 an average three rings in transverse section, may 

 according to the notes of Mettenius^ belong to 

 this category. Of the three rings the outer con- 

 sists of numerous filamentous bundles, the two 

 others of broad and flat ones. These stems how- 

 ever require more exact investigation. The same 

 may be said of the inverted conical-shaped thick 

 tuberous stem of Angiopteris evecta^, of which 

 INIettenius has thoroughly investigated and de- 

 scribed one large specimen only. Transverse 

 sections of the stem show 5-6 irregular zones or 

 rings which pass over one into another. From 

 an irregular network of bundles surrounding the 

 pith bundles arise in a succession correspond- 

 ing to the arrangement of the leaves, and pass 

 obliquely upwards and outwards; each of these 

 soon becomes wider, and splits into a rather ir- 

 regular network rising obliquely outwards and up- 

 wards, and having the form of a portion of a conical 

 surface, the bundles of which are reticulately con- 

 nected with those of neighbouring equivalent por- 

 tions. A number of branches, derived from that zone which is at the time the outer- 

 most, enter the base of each leaf (into the back and sides of its basal part), and, 

 to take the place of those which have passed out, a corresponding portion of the 

 next inner zone passes upwards into the outward zone from below the axils of the 

 leaf in question, and of the two next lower lateral leaves. Portions of the third zone 

 enter the gaps thus formed in the second, and are reticulately connected with the next 

 outer zone. Further anastomoses between the branches of the successive zones are 

 formed at the very point of insertion of the leaf, and two bundles belonging to the inner 

 side of the base of the leaf are given off from the second zone, which enters the gaps of 

 the outer zone. In the stems investigated the lower zones had small, almost cylindrical 

 bundles, which formed wide-meshed irregular nets; the upper zones (near to the 

 stationary end of the dead stem) had broad flattened bundles with narrow reticular 

 meshes ; the zones of intermediate position were also intermeaiate as regards the reticular 

 form ; the bundles which enter the leaves were of similar form to those of the zones from 

 which they arose. Accordingly transverse sections showed at different heights either 

 several concentric annular zones, often irregularly connected by oblique bands (the 

 portions cut through in their course into outer zones), consisting of small roundish 

 bundles separated by abundant parenchyma — corresponding to the usual arrangement in 

 the tuberous stems of Marattiaces; or on the other hand rings, of which the outer at 

 least consist of broad flattened pieces, separated by some few bands of parenchyma. F"or 

 further peculiarities, comp. Mettenius, Lc. 



Fig. 137. — Saccolonia adiantoides ; transverse sec- 

 tion through the stem; after Mettenius; natural size. 

 At a the band-like vascular bundle of a leaf, just 

 separated from the outer rin;^ ; d and c bundles of two 

 successively higher leaves, appearing as protrusions of 

 the outermost ring. The bundles which enter the leaves 

 are finely undulated. The bundles of all rings are sur - 

 rounded by a sheath of darker, thicker walled paren- 

 chyma. In my specimens the inmost ring of bundles is 

 sometimes narrow, sometimes it is replaced by a single 

 round btmdle. 



* I.e. p. 524. — Compare also Brongniart, Archives du Museum d'llist. Nat. torn. 1. p. 439, Tab. 

 XXXIII, and Karsten, Vegetationsorg. d. Palmen, Taf. IX. fig. 10. 

 '' Brongniart, /. c. 



