606 FILICALES 
which, however, soon develops a pith. The anatomy of this Fern, which 
deserves a thorough reinvestigation, appears to be comparable with that 
of a solenostelic Dennstaedtia: it suggests the structure from which the 
more complicated Cyatheaceous stems may have arisen. Another species 
with exceptionally simple structure is stated to be A. dlechnozdes, which is 
peculiar in having a trailing axis. 
In the vast majority of the Cyatheae the vascular system consists 
essentially of a dictyostele, with accessory strands in the pith, and in 
some cases in the cortex also. The leaves being closely disposed on the 
massive axis, the leaf-gaps, which 
are narrow, overlap, and accord- 
ingly several are traversed in a 
single transverse section (Fig. 
337 B). The dictyostele is thus 
represented by several broadly 
strap-shaped tracts, with their 
margins turned outwards, and 
guarded on either side by bands 
of brown slerenchyma: this is 
the correlative of the solenostele 
of simpler types. The _leaf- 
trace, composed from the first 
of numerous distinct strands, 
springs from the margin of the 
leaf-gap, the strands being dis- 
posed in the usual horse-shoe 
series. But over and above 
this fundamental vascular system 
Fic. 337 B. # accessory strands are found in 
Cyathea lmrayana, Hook. Transverse section of stem. the pith (Figs. 337 Ay B): these 
Natural size. At, c, d, foliar gaps ; all the black bands and Are : 
spots are stereom, all ‘the paler bands are vascular strands originate from the foliar gaps, 
in section. The letters a, s, s’, {have the same meaning as H 
iy Mia sepa, (anor Be Peek) and traverse the pith as a 
branched system with occasional 
blind endings. In origin and nature they would appear to be comparable 
to the accessory rods seen within the solenostele in Dennstaedtia rubiginosa 
(compare Fig. 333).2 In the cortex also an accessory series of strands, 
related to the leaf-trace, is found: it is well shown in C. /mrayana 
in Fig. 337 ¢, and is reported also for other species, both of Cyathea 
and of Alsophila. This cortical system has no recognised correlative in 
other Ferns. 
Young plants of Alsophila excelsa have been examined by Gwynne- 
Vaughan,’ with a view to tracing the ontogeny of the vascular system, and 
especially the origin of the medullary strands: his results are illustrated 
1Mettenius, Ueber Angiopterts, p. 524, note 3. 
2 Gwynne-Vaughan, Z¢., p. 709. 3 L.t., Pe 709. 
