On a Branched Cone of Equisetum maximum. 115 
hese appear to be arranged as portions of a ring as indicated in 
Fig. 20 a. 
e 
D 
Fig. 20. a, Diagram shewing the position of the medullary strands, r, nor¬ 
mal ring of bundles; m, medullary strands; b, c, d, Transverse sections of 
bundles in the pith, x 100. e, side of the bundle towards the periphery of 
the cone ; i, side of the bundle towards the centre of the cone cone ; t, 
tracheids ; a, thick-walled parenchymatous cells on the outside of some of 
the bundles. 
Fig. 20c shews the appearance usually presented by these 
medullary bundles in transverse section. They are generally more 
or less circular and consist of a few tracheids (Fig. 20c, t) scattered 
irregularly among small-celled parenchyma. On the inner side 
they pass gradually into the ground-tissue of the pith, but the side 
towards the periphery of the stem is generally bordered by some 
thick-walled parenchymatous cells (Fig. 20c, a). No evident phloem 
could be made out. 
