Bower . — Studies in the Phytogeny of the Filicales. 377 
(D) Blechnum attenuatum (Sw.), Mett. 
This is a species which is sometimes creeping in habit, but more usually 
erect, and may often assume a climbing habit, attaching itself by means of 
roots to the stems of larger plants. Material was obtained in Jamaica, and 
also from the Botanic Gardens of Edinburgh and Glasgow. The axis 
contains a dictyostele, with very numerous, narrow leaf-gaps. In Text- 
fig. 4 there are thirteen of them, and they have been numbered, according 
to their position in the circular dictyostele. As their number is so large 
their succession from below and their relation to the leaf-traces and root- 
traces may be readily deduced. 
The large meristele between gaps 9 and 10 is preparing to give off 
a root-trace by separation of a central tract of the meristele. The process 
is shown more advanced in the meristele on 
the opposite side of the axis, which is 
beginning to form by involution the gap 
numbered 1. The central tract of the 
meristele is here nearly separated, while 
in the case of gap 4 the separation of 
the root-trace is seen completed, and thus 
the foliar gap is fully formed. From the 
meristeles on either side of a gap thus opened 
a strap-shaped leaf-trace strand is then given 
off, as seen in gaps 8 and i 2. These very 
soon divide each into two (see gaps 6 and 
10), and later into larger numbers (gaps 
5, 7, 9). It is thus evident that the vascular 
System is on the Same plan as that of bered for convenience 0 of reference, 
B. tabular e, but complicated by a greater ^ oe “°^ in x or 4 der of their natural 
crowding of the leaves, and a much larger 
proportion of vascular tissue, as seen in the transverse section. This, 
together with the relatively large bulk of the strands, is in accord with 
the climbing habit, and affords an interesting basis for comparison with 
the climbing Stenochlaena . It corresponds to B. tabulare in having 
a single root arising from the base of each gap, and in the fact that the 
leaf-trace consists originally of only two strands. 
The mature fertile pinna of B. attenuatum shows an outline as seen in 
PL XXIV, Fig. 7, e. There is no marked flange, but the whole section is 
roughly four-angled, owing to the presence of two rounded ridges, right 
and left of the midrib. The latter is traversed by two vascular strands, 
with a slight surface-involution between them. Right and left of this are 
glands (hydathodes) of flask-like form, opening upon the adaxial surface. 
To each of them a vascular strand passes ; it is derived from the commissure 
Text-fig. 4. Blechnum atienn- 
atum (Sw.), Mett. Transverse section 
of the stock : the leaf-p-aos are num- 
