400 ROYAL SOCIETY OF CANADA 
which does not seem to arise by the absorption of the protoxylem elements 
as in the case of the canals in the bundles of Equisetum.” 
Strasburger, on the other hand, expresses a contrary view, and is 
supported by other observers (19, 464). “ Von Jancewski firmly estab- 
lished for Iscetes Durieui that the intercellular passages on the inner side 
of the bundles arise from the protoxylem, whose disorganisation begins 
at a very early stage. The same has been proven in isolated cases by 
Kruch. In short, the intercellular passages on the inner side of the 
bundles always originate from a tracheid cell, which, developing into 
a protoxylem element becomes quickly absorbed.” 
Thyloses are not recorded for these, although they could probably 
be induced in the same manner as in Equisetum. 
Intercellular passages adjacent to the protoxylem are of wide oc- 
currence in the Monocotyledons (3, 326 et seq.) and it is interesting to 
note that under certain induced conditions thyloses make their appear- 
ance in them. ‘The following observations by Miehe (8, 547) in the 
course of an article on geotropism established this fact:— It is a fact 
that abnormal manifestations of growth may arise in the case of wounds. 
The extension of thylose formation affords us a means of determining 
(Zu prufen) the area affected by the wounds. In the internodes of 
Tradescantia fluminensis there arise, through the rupture of several 
annular and spiral tracheids, lacunæ which extend the whole length of 
the Internode, and, in transverse section, appear as spaces of irregular 
contour. Rings of living cells surround them, the ruptured annular 
and spiral fragments lying scattered in the cavity. They are closed 
above and below by the plates of nodal tissue. In case these are dam- 
aged, the living cells bordering the passages begin to grow out, and fill 
them up to a greater or less extent with a bladder-like tissue. At times 
these growths extended even to the third joint (Gelenk), and thus 
showed that even at this distance the wound had still influenced an 
abnormal growth in isolated cells.” He then goes on to discuss the effect 
the wounding has on geotropism. 
What he terms the wound, is in this case a cut effected by means of 
a double knife at a certain point in the stem, the method he employed 
being fully described in his paper. It will be shown below that the ap- 
pearance of the thyloses here is due primarily to the same causes as in 
the forms mentioned above, the cut being merely an indirect means of 
inducing them. 
A similar appearance was noted by Mellink (8, 750, and Figs 4 
and 1a) in petioles of Nymphæa alba which had been wounded in the 
course of growth. The thyloses arose from the cells surrounding the 

