MORPHOLOGY OP PHYLLOGLOSSUM DRUMMONDII. 
673 
It has been above stated that the mature leaf is of simple form, and almost 
cylindrical: a transverse section of it shows an almost circular outline, limited 
peripherally by a more or less regular epidermis, in which are numerous stomata of 
simple structure, and distributed uniformly on all sides (fig. 36). Below the epidermis 
is a massive, thin-walled mesophyll, arranged almost uniformly all round : there are 
large intercellular spaces, and respiratory cavities. The more peripheral cells have 
their longer axis disposed obliquely to the outer surface (fig. 37), while in those which 
are nearer the centre of the leaf the longer axis is directed longitudinally : thus in 
the transverse section the cells nearer the centre of the section appear almost circular. 
At the centre of the transverse section there is a small and simple vascular bundle, 
consisting only of four or five xylem elements, surrounded by tissues with cellulose 
walls, and small cell-cavities with protoplasmic contents. Longitudinal sections show 
that the xylem elements are elongated, with annular or irregular spiral thickening : 
there is no clearly marked phloem, and no bundle-sheath. The more central portion 
of the mesophyll consists of elongated and pointed elements (fig. 37) ; the oblique 
terminal walls where two such elements adjoin one another are of irregular thickness, 
and as seen in surface view are marked with shallow pits: there is no special 
character of their cell-contents, and a nucleus is present. It seems probable that 
this tissue replaces the phloem not only anatomically, but also physiologically, in fact 
that it is a rudimentary type of phloem. It is thus seen that the vascular bundle of 
the leaf is of a very simple type. 
A peculiarity of structure is to be noted in the parenchyma at the base of the leaf. 
There the intercellular spaces are large, and into them there project numerous peg¬ 
like outgrowths from the walls of the adjoining cells (fig. 40) ; these are similar to 
those already well known as existing in the parenchyma at the base of the leaf in 
many ferns. The substance of which they are composed gives the following reactions: 
(1) They swell slightly with strong potash solution, and become less highly refractive, 
but do not lose their clearly defined outline ; they do not stain with Schulze’s 
solution, even after previous treatment with potash, though the adjoining walls give 
a deep blue stain ; (3) in sulphuric acid they behave similarly to the middle lamella, 
that is, they resist its action longer than the layers adjoining the protoplasm ; (4) 
with methylene blue they stain very slightly or not at all. From these reactions 
it is clear that the outgrowths are not composed of ordinary cellulose ; but it is 
difficult to define what their substance really is ; it would appear, however, that it is 
not slightly cuticularised cellulose, such as described by Luerssen for similar out¬ 
growths in ferns.* 
A transverse section of the peduncle, or sporangium-bearing axis, shows an 
epidermis with stomata; its outer wall is thick, and is covered with cuticle, and a 
narrow cuticularised layer. Beneath the epidermis is parenchyma, with large inter- 
*“TJeber Intercellularverdicbungen im parencbymatischen Grunclgewebe der Fame.” Sitzungsber. 
der naturforsuh. Gesellschaft za Leipzig, 1875, p. 70. 
