'^f^ 



VA SC ULA R CR YP TOGA MS. 



end each bundle splits into two short diverging arms, by which it unites with the 

 two neighbouring bundles of the next lower internode, where they descend into 

 it from their sheath-teeth. The joints of the stem and their leaf-sheaths therefore 

 alternate; and since in each joint the arrangement of bundles, leaf-teeth, projecting 

 longitudinal ridges, and depressions or furrows, is exactly repeated in the transverse 

 section, the different parts of a joint always correspond to the intervals between 

 the homologous parts of the next upper and next lower joint. If the internode 

 has projecting longitudinal ridges on its surface, one of these always runs down- 

 wards from the apex of each leaf-tooth parallel with the others as far as the 

 base of the internode ; between each pair of leaf-teeth commences a furrow or 

 channel, which also continues as far as the base of the internode. The projecting 



Fig. itz a.—Eqnisetnm Tebnateia; A piece of an upright stem (natural size), i t' intemodes, k its central cavity, 

 I lacunre of the cortex. 5 leaf-sheath, :: its apex, a a' a" the lower intemodes of young leaves ; B longitudinal section 

 of a rhizome (X about 2), k septum between the cavities h A, .4' fibro-vascular bundle, / lacunae of the cortex, S leaf- 

 sheath ; C transverse section of a rhizome (x .about 2), i> and / as before ; D union of the fibro-vascular bundle of an 

 upper and lower internode z i\ A' the node. 



ridges lie on the same radii as the fibro-vascular bundles, each of which contains 

 an air-canal; the depressions or furrows lie on the same radii as the lacunae of 

 the cortical tissue (which are sometimes wanting), and alternate with the fibro- 

 vascular bundles. The branches and roots spring exclusively from within the 

 base of the leaf-sheath; and as this forms a whorl, the branches and roots are 

 also verticillate. The branches are all of endogenous origin ; they arise in the 

 interior of the basal tissue of the leaf-sheath, upon radii of the stem which alter- 

 nate with the fibro-vascular bundles, and thus also with the teeth of the sheath. 

 A root may arise beneath the bud of each branch ; both break through the leaf- 

 sheath at its base. All the joints of the axis agree in these respects, however they 

 may be modified as underground rhizomes, tubers, ascending stems, leafy branches, 

 or sporangiferous axes. 



