88 G wynne- Vaughan . — Observations on the 
reticulated. They contain a fair amount of protoplasm and 
a conspicuous nucleus. Cells somewhat similar to these 
were first mentioned by Dippel 1 * in Osmunda and Cyathea ; 
he regards them as reservoirs for bye-products such as resin, 
tannin, &c., but in Loxsoma no trace of these substances is to 
be detected. The tissue described by Russow 3 in Marsilea 
under the name of cavity-parenchyma (Luckenparenchym), 
and again by Thomae (l.c.) in Angiopteris and Cyathea under 
the title of ‘ Stumpfzellstrange, 5 is almost identical with that 
in Loxsoma. Thomae also states that the papillae may become 
cut off by walls from their mother-cells, on which account 
he compares this to a case of thylosis. Other examples have 
recently been given by Seward in Matonia pectinata ( 1 . c.), 
and by Farmer 3 in Helminthostachys ; indeed it has been 
mentioned by various observers as occurring in all the main 
families of Ferns, although the exact limits of its distribution 
are yet to be determined. 
Towards the top of the petiole the vascular strand, although 
still resembling a horseshoe, is markedly different from the 
form already described. Taking it, for instance, at a point 
just below the insertion of the lowest branches of the leaf 
(Fig. 7, b), it is seen that the flanks of the horseshoe are 
much wider apart from each other, and that its concavity 
is more shallow ; in fact, the whole meristele appears to be 
somewhat flattened out. The departure of the vascular strands 
for the successive branches, which are nipped off from the 
ends of the arms of the meristele, does not materially alter 
its form, although causing it to decrease considerably in 
size. At the same time, however, the hooks at the ends 
of the xylem-curve gradually disappear, and the protoxylem- 
groups become fewer in number until three only are left ; 
one at the end of each arm and one in the median region 
of the curved xylem (Fig. 7, c). From now onwards, this 
median protoxylem sinks further and further away from the 
1 Das Mikroskop, Theil ii, p. 201, Fig. 100, 1867. 
3 Loc. cit., pp. 6 and 101, and Taf. ii, Fig. 13. 
3 Ann. Bot., vol. xii, no. 51, p. 439, 1899. 
