Boodle— Anatomy of the Schizaeaceae. 377 
In Schizaea digitata a comparison of transverse sections of 
the young stem at different stages of development points to 
a possibility that the endodermis, pericycle and phloem may 
be formed by subdivision of a single layer. This would be 
a very remarkable case of stelar endodermis, or cortical 
phloem, and it is intended to reinvestigate it. 
Schizaea, petiole and node. 
A transverse section of the petiolar bundle of Schizaea 
digitata is represented in Fig. 13. The bundle is seen at 
once to be collateral. There is a band of xylem on the 
morphologically upper side, with no well-marked protoxylem, 
but judging by the size of the tracheides those laterally 
placed are probably the first to differentiate. This section 
was cut near the base of the petiole, and spiral elements 
appear to be absent in this region, the tracheides being 
scalariform. The phloem forms a band on the lower side 
(flh'.), and consists of thick-walled sieve-tubes and a certain 
amount of parenchyma. A group of fibres (/.) is seen touch- 
ing the xylem at each end of the bundle. Their end-walls 
resemble sieve-plates and they, appear to represent lignified 
sieve-tubes. The pericyclic cells are rather thick-walled as 
in the stem, but have been represented as thin- walled in the 
figure. Sections of a young petiole cut higher up than the 
level of the section just described, prove that spiral protoxy- 
lem-elements are formed on the upper side of the bundle 
roughly in the median region (Fig. 14,/^'.) and the differentia- 
tion proceeds outwards on both sides along the periphery of 
the xylem, so that a crescent of tracheides is formed, the 
more centrally placed tracheides developing subsequently. 
The nearly median first-formed tracheides become crushed 
rather early, and are scarcely distinguishable in the mature 
petiole. In the lamina of S. digitata the bundle in the 
midrib resembles the bundle of the petiole, but has more 
numerous fibres. In the median region on the lower side, 
in the sections examined, three pericyclic cells had become 
much enlarged, and had crushed the greater part of the 
