497 
of Schizaea malaccana. 
phloem, has practically no nucleated cells between its elements. 
The tracheids themselves are narrow ; their thickening is 
scalariform or slightly reticulate. There is no trace of spiral 
elements anywhere in the stem. 
The centre of the stele inside the xylem is one of the great 
features of interest in this species. In the simplest case 
there is a homogeneous ‘ pith ’ consisting of living thin-walled 
parenchymatous cells, of about the same, or rather greater, 
diameter than the tracheids, and of approximately the same 
length as the latter, seen in longitudinal section. This 
tissue has nothing in common (except its position) with the 
tissue enclosed by the internal endodermis of a solenostele. 
It is undoubtedly an £ intra-stelar pith,’ as Russow and Prantl 
held. 
Sometimes, though rather rarely, there appears in the midst 
of this central parenchyma a strand, or more seldom two 
strands, of tracheids, rarely more than two or three in a 
strand as seen in transverse section, and quite distinct from 
the xylem-ring (Fig. 4, int. tr.). Followed up in a series of 
sections, it is found that these strands are sometimes quite 
isolated, and sometimes connected at one end with the xylem- 
ring, while the other end has a blind termination in the 
parenchyma. The arrangement of these strands appears to 
have no relation whatever to the leaf-traces, and in fact to 
be quite capricious. The tracheids themselves are quite 
normally developed, and are identical in structure with those 
of the xylem-ring. These internal tracheids are only found 
in the larger steles where there is a comparatively bulky 
pith. In one specimen from Perak, kindly given us by 
Mr. R. H. Yapp, a considerably larger number of internal 
tracheids occurred at a certain level, forming an almost 
complete band across the pith (Fig. 5). Higher up, the stem 
dichotomized, but the phenomenon in question had no direct 
connexion with this, for the internal tracheids all disappeared 
before the stele began to divide \ 
The discovery of internal tracheids in the pith of the stele of Schizaea was 
made by Mr. Boodle in S. dichotoma before we found them in the present species. 
