the Secretory Tissues of the Marattiaceae. 419 
Marattia attenuata ; and in the petiole of Danaea simplicifolia , Marattia 
alata , &c., &c. 
They are less frequently associated together in irregular groups, e. g. in 
the stem of Danaea nodosa (Text-fig. 11), and in the sporangium wall 
of Kaidfussia aesculifolia , &c., &c. 
It sometimes happens that the parting-walls of adjacent tannin-cells 
break down, the solution of the wall beginning in the centre and gradually 
spreading until a typical vessel or duct is formed, e. g. in the petiole and 
root of A 7 igiopteris evecta (Text-fig. 10, and cf. Farmer, L c., p. 369 and 
PI. XV, Fig. 13), and in the root of Marattia attenuata. The breaking down 
of the parting-walls bears no relation to the age of the cells; it may take 
place either in very young or in fairly old tissues. 
Such a series of stages in the development of a typical tannin-duct was 
described and illustrated by Lutz ( 1 . c., pp. 134, 135 ; Pl. II, Figs. 3-7), who, 
however, mistook these tannin-ducts for lysigenous mucilage-canals, and 
stated that the tannin was eventually replaced by mucilage. 
I was quite unable to confirm this explanation, since in all my material 
the tannin-cells (or ducts) are from the very beginning absolutely distinct, 
and, even in old specimens, bear no resemblance to the mucilage-canals. 
Whereas the mucilage-canals freely branch and anastomose (Fig. 5), the 
tannin-ducts seldom branch and never anastomose. 
From our knowledge of the chemical composition of these secretions it 
would appear very improbable that one should be converted into the 
other; notwithstanding that in certain Angiosperms tannin occurs associated 
with mucilage. 
In the stem of Danaea nodosa and in the sporangium wall of Kaul- 
fussia aesculifolia irregular tannin-containing cavities are produced by the 
breaking down of the parting-walls between adjacent tannin-cells. 
A true secretory epithelium is never present round the tannin-cells 
or tannin-ducts, but their contents often exert a considerable pressure upon 
the surrounding cells, which are slightly crushed and assume the appearance 
of an epithelium, to which, however, they bear only a superficial resemblance. 
On the other hand, the tannin-cells (or ducts) are often compressed by 
the surrounding parenchyma (Text-fig. 9 ; Figs. 4 and 5). 
Tannin-sacs are abundant in the ramenta of Angiopteris evecta , Danaea 
nodosa , Danaea alata (Text-figs. 13 and 13), Marattia Cooperi , and Marattia 
fraxinea ; in the characteristic two-celled hairs of the petiole of Kaulfussia 
aesculifolia (Text-fig. 14); and in the paleae of Archangiopteris Henryi. 
Wound-tannin. A copious secretion of tannin was observed in the 
immediate neighbourhood of wounds. In this respect the tannin may 
be compared with the secretion of resin which is induced by traumatic 
stimuli in certain Conifers. 
Theoretical considerations . In all the genera of Marattiaceae examined 
