420 
VA'iCULAR CRYPTOGAMS. 
Histology. As a peculiarity of the epidermal tissue the very large, widely-open 
stomata of the leaves of Kaulfussia may be mentioned. They are developed in the usual 
M'ay, but they soon become remarkable on account of the extraordinary size of the 
aperture and of the arrangement of the guard-cells in a narrow ring, surrounded by 
two or three rings of epidermal cells (Luerssen). 
In the intercellular spaces of the parenchymatous ground-tissue of the leaves Luerssen 
found outgrowths from the walls of the surrounding cells. Where the spaces were small 
these outgrowths assumed the form of bosses or pegs, but where the spaces were 
large they were long thin filam3nts. They are quite solid and consist of cuticularised 
cell-membrane. The large intercellular spaces are quite filled with a felt-work of these 
filaments. Luerssen found this to be the case in Kaulfussia^ Dancea, Angiopteris, 
Marattia. 
In the ground-tissue of the leaves bands and bundles of sclerenchyma are differen- 
tiated, but it is not so hard or so darkly-coloured as that of Ferns. In the articular swellings 
collenchyma is developed. Elongated cells containing tannin are to be found in all parts 
of the ground-tissue, and gum-ducts are scattered throughout the thin-walled paren- 
chyma. Reference has been made on page 64 to the Sphaerocrystals. 
In the stem of Angiopteris, which I have investigated, there is no sclerenchyma. It 
consists for the most part of large thin-walled parenchymatous cells, amongst which are 
scattered very numerous cells containing tannin, as well as gum-ducts. The contents of 
the latter cover a piece of the stem when placed in water with a thick layer of 
gelatinous mucilage. 
The fibro-vascular bundles of the leaves and of the stem resemble those of the Ferns. 
The central xylem consisting of wide scalariform tracheides is surrounded by a layer of 
phloem. In the leaf the bundles (of Angiopteris) are usually flattened, in the stem they 
have a circular outline. The usual bundle-sheath, consisting of a single layer of cells with 
a peculiar folding on their adjacent walls, which is especially constant in the Ferns, is 
absent in Marattia and Angiopteris from the fibro-vascular bundles both of the leaf and of 
the stem, but it is present in Danoea. In the root it is present, and consists of large cells. 
Harting has described the roots which traverse the parenchyma of the stem (Fig. 291 
A, av) as fibro-vascular bundles, and has figured them on Plate VII. figs. 3 and 4 of his 
Monograph of the Marattiaceae. He did not investigate the structure of the real fibro- 
vascular bundles at all. It is necessary to draw attention to this mistake because Russow, 
relying upon Harting, describes the fibro-vascular bundles of the stem as possessing an 
external sheath (Scbutzscbeide), and states that this structure occurs only in the roots 
which traverse the stem. It is difficult to imagine how Russow could have overlooked this 
obvious mistake of Harting's. It is by no means easy (in Angiopteris) to obtain a 
transverse section of one of the fibro-vascular bundles of the stem, for they are very 
irregularly curved and are everywhere covered with roots which traverse the network 
formed by the bundles. As I had only one stem at my disposal I was unable to satisfy 
myself as to the true form of the fibro-vascular system, but it appears that Harting's 
figure is not very true to nature. The numerous bundles which bend outwards into each 
leaf are formed by the division in the lower part of the petiole of the few bundles which 
spring from the fibro-vascular network of the stem (Fig. 291 A). 
According to Holle, the stem of Marattia grows by means of a four-sided apical cell. 
In the stouter roots, according to Harting and Russow, the place of the apical cell is 
taken by a layer of very large cells. In the slender roots of Marattia and Angiopteris 
Holle has found a four-sided apical cell. 
