420 VASCULAR CRYPTOGAMS. 



Hhtology. As a peculiarity of the epidermal tissue the very large, widely-open 

 stoinata of the leaves of Kaulfussia may be mentioned. They are developed in the usual 

 way, 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 filaments. 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^ Danoea, 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 Dancea. 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, q.v) 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 [Schutzscheide), 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. 



