Maslen. — The Relation of Root to Stem in Catamites. 71 
On the whole, we incline to the opinion that the larger adventitious 
roots of Catamites , i. e. those which spring directly from the stems, were 
probably fistular, and the presence of thinner-walled central cells would 
indicate that this may have been their natural condition. A few of our 
specimens form an exception to this rule. The sections from which Figs. 
2, 3, 4, 5 are taken show roots originating directly from a stem, but the 
pith of the former is neither differentiated nor hollow. This may be a 
specific distinction. 
This paper is not specially concerned with the smaller roots of 
Catamites , of which there are many scattered through our sections, and 
which are mainly branches of roots and not borne directly on stems. These 
are the specimens usually figured by Williamson, and by Williamson and 
Scott. The medulla varies enormously in relative size, and is sometimes 
absent altogether. As usually developed, the pith-cells show a gradual 
increase in size towards the centre, but no differentiation into distinct outer 
and inner portions such as is commonly seen in the larger roots, and there 
is no evidence that the pith became hollow. The presence or absence of 
a pith in these small specimens of Astromyelon appears to be an individual 
variation, or it may vary in the same individual. A curious case is illus- 
trated in Fig. 13 (slide 48 M), which shows a small branching specimen 
in which the branch has a conspicuous pith while the parent axis has 
none. 
Summary and Conclusions. 
The roots of Catamites were mainly adventitious, and they usually 
arose in whorls from the nodes of the lower portion of the aerial stems as 
well as from the underground rhizomes. 
The lowest portion of the ascending stems rapidly tapered to their 
insertion, probably, on the underground rhizome. The actual connexion 
was probably a small one. The roots arise in direct connexion with the 
protoxylem of the main axis, and are not seated on the bases of the 
branches as in Equisetum. Detailed examination of this large series of 
sections affords no evidence of any connexion between the roots and the 
infra-nodal organs of Williamson. Roots and stem-branches are difficult 
to distinguish from one another in sections which are cut quite near to their 
insertion on the protoxylem of the main axis. The roots resemble the 
stem-branches in their position relative to the stem-bundles and the out- 
going leaf-traces, as seen in tangential sections through the main stem, i. e. 
in both cases the lateral member is usually placed so that its centre lies 
vertically above a medullary ray of the internode below and between two 
leaf-traces. 
The roots arising directly on the stems appear to differ from stem- 
branches in the following particulars; — The roots arise on a level with 
