70 Maslen—The Relation of Root to Stem in Catamites. 
characters which led Williamson to separate it from Catamites (i. e. the 
root from the stem), and the smaller specimens usually agree in the posses- 
sion of a solid medulla either relatively small or large. In the larger 
examples, however, those which arise directly on the stems, the disappear- 
ance of the central part of the pith is usual, and there is often a definite 
line separating the central cavity from the peripheral persistent portion. 
The latter always forms a wide band of tissue, and the pith never dis- 
appears right up to the xylem as is usually the case in the larger stems. 
Some slides that we have serve to throw some light on this subject. 
Fig. 9 (slide 1685 S) is from an approximately transverse section of 
a stem which is evidently cut near to (just below) a node, as some infra- 
nodal organs (i. n. 0.) are passed through. A root is shown passing out 
obliquely through the secondary wood (s.x.) of the stem. This root must 
have passed out much more obliquely than those shown in Figs. 2, 3, 4, 5, 
and 6, since although the stem is cut nearly transversely the root is also cut 
more nearly transversely than longitudinally. The connexion of the wood 
of the root with the secondary xylem of the stem is clearly seen, as well 
as the contortion of the tracheides ( c . t.) on the inner side of the root. 
The pith of the root is here quite entire, but it shows a well-marked 
differentiation into a small central portion (c.p.) of thin-walled cells and 
a wide peripheral zone (/>*/.) in which the cells appear to have had thicker 
walls* 
Fig. 10 shows a portion of Fig. 9 more highly magnified. The 
differentiation of the pith and the contortion of the tracheides are more 
clearly shown. 
Fig. 11 (slide 1748 S) is from a slide cut from the same specimen as 
Figs. 9 and 10. The root is now farther out, and the central portion of 
the pith is represented by a space, owing to the destruction of the thinner- 
walled tissue. 
Fig. 12 (slide 22 M) shows a root cut quite close to its origin. The 
connexion of the primary and secondary wood of the stem with those of 
the oot can be seen, and also clear differentiation of the pith into an outer 
thicker-walled zone (p. pf and a thinner-walled central portion (c. pi). 
In other sections showing the same root cut farther out from the axis 
the central part of the pith is hollow. 
The differentiation of the pith is visible in a large number of the 
sections at our disposal, and in nearly all cases the central portion becomes 
hollow while the root is still embedded in the parent stem. In some cases 
there is no evidence to show that the destruction of the central cells was 
other than a natural process, but in other cases fungal action appears to 
have caused or helped in the disintegration. It may be that the walls of 
the inner cells were composed of cellulose, while those of the outer part 
were more or less lignified and so were able to resist fungal action. 
