74 PROTOPTERIS. 
preserved petiole bases of P. Witteana and those of Dicksonia 
antaretica. 
Between the prominent petiole scars the matrix of the fossil is 
somewhat lighter in colour, as at a.a., Figs. 1-3; this appears to 
consist of elongated parenchymatous cells, which may possibly 
have originally existed as multicellular filaments, but have 
been more or less welded together in the process of mineralization. 
Here and there in this inter-petiolar tissue traces of adventitious 
roots occur, as e.g. at r and 7” in Figs. 1-3. 
In Dicksonia antarctica the bases of the petioles are separated by 
a woolly mass of brown threads, traversed by a few adventitious 
roots. If these threads (ramenta) be examined microscopically 
they are found to be made up of long and narrow parenchymatous 
elements, very similar in shape to those which occur between the 
petiole bases in the fossil stem. 
In Pl. XI. Fig. 2 a transverse section of the fossil stem is repre- 
sented natural size; the curved band-form vascular plates are 
clearly shown at ¢, and at p portions of the conducting tissue are 
curving outwards as leaf-traces; an impression of a root section is 
seen at 7, and at a are the masses of tissue separating the individual 
petioles. 
A small piece of the vascular tissue of the stem is shown in 
Fig. 4; the xylem, 2, is made up of polygonal tracheides of the 
scalariform type, and associated with these there are indications 
of parenchymatous cells; the whole xylem tissue being apparently 
very similar in structure to that in the stem of Dicksonia antarctica. 
The dark lines, 3.6, on either side of the xylem no doubt mark 
the limits of the phloem, but this more delicate tissue has not been 
preserved. 
In a few places there are traces of fairly large brown-walled 
elements external to the limits of the phloem. 
The xylem of this specimen, as regards the arrangement of 
the vascular bands and their histological structure, is very 
similar to that of Protopteris Cotta as figured by Corda.' 
V. 2181. An imperfectly preserved Sandstone cast. Leaf-scars 
indistinctly shown. Ecclesbourne. Rufford Coll. 
1 Flor. Vorwelt. pl. xlix. 
There is a section of P. Cottai in the Botanical Department Collection (British 
Museum) cut from the specimen figured by Corda. 
