12 
Isabel Browne. 
Pig. 3), for E. maximum and E. silvaticum by Leclerc du Sablon 
(11, Figs. 15 and 17), and for the fossil Equisetum for Equisetites) 
stellare Fritel and Viguier, from the Sparnacien by Fritel and 
Viguier (8, Text-Fig. 5 and PI. IX, Fig. 3). Text-Fig. 1 a 
represents such a bundle of the tuber of E. silvaticum. It is 
copied from Leclerc du Sablon and the xylem is shown in black, in 
order to bring out its distribution more clearly. Except those of 
E. arvense , all the bundles of tubers that have been figured show 
essentially the same irregular distribution of tracheides, inter¬ 
spersed with small groups or bands of parenchymatous cells, 
though in the bundle of the fossil Equisetites stellare the cells, 
vascular and parenchymatous, are more numerous. According to 
Milde’s figure the bundle of the tuber of E. arvense is also of this 
type, but in Ramey’s figure of such a bundle the xylem consists of 
a solid group of 16 thick-walled tracheides. 
Text-Fig. 1. (a) Transverse section of a vascular bundle of a tuber 
of E. silvaticum, after Leclerc du Sablon. Magnification not stated. 
(b) Transverse section of the third internode of the primary axis of E. maximum, 
er Buchtien. x216. 
In the internode of the primary axis the xylem of each 
bundle forms a single group. This is shown in Text-Fig. 1 b., 
representing a transverse section of an internode of the primary 
axis of E. maximum, Lam. The figure is copied from Buchtien 
(4, PI. 5, Fig. 119) and again the xylem has been filled in in black. 
The wood of each of the small bundles consists of five to ten, on 
average of eight tracheides. In the more reduced bifascicular 
primary axis of E. variegatum, figured by the same author, each 
bundle contains four or five rather small tracheides, irregularly 
embedded in parenchyma (4, PI. 5, Fig. 118). 
But even in the internodes of the aerial stems of Equisetum 
the structure of the bundle is not always uniform. For the two 
postero-lateral groups of metaxylem are not always separated from 
the more deeply-seated carinal group of protoxylem. A study of 
