370 ROYAL SOCIETY OF CANADA 
In a stipe about 18 cm. long and about 0.4 cm. in diameter, the fol- 
lowing was noted in sections taken from the tip to the base. Unless 
otherwise indicated, all the sections are cut transversely. 
The sections at the tip show the tissues in a very immature condi- 
tion, and full of protoplasmic contents, so that in all the tissues except 
tha protoxylem the cell walls are so thin as to be almost invisible and 
the living protoplasm stands out strongly. The cells of the protoxylem 
are clear of contents and exhibit definite, thickened cell-walls. 
All the vascular bundles of the sections in this region show the 
protoxylam elements more or less separated from one another, and in 
many cases definite canals can be seen, the protoxylem elements border- 
ing on the cavity. In other cases the canals are not yet fully formed, 
and the separated protoxylem elements fill the cavity almost completely 
(Photo. 1). 
In longitudinal sections the very immature condition of the tissues 
is shown even more clearly, there being no sign of any secondary xylem 
with thickened walls,—elongated cells full of protoplasm occupying 
their later position. 
The protoxylem is seen to consist of spiral and annular tracheids, 
which are for the most part disorganised, and le in the cavity of the 
longitudinal canal formed by the splitting and disintegration of the 
tissue (Photo. 2, Photo. 3). The spirals are frequently observed un- 
coiled and present the appearance of cells which are giving forth pro- 
trusions, the seeming protrusions being partly uncoiled portions of the 
spirals. This is the appearance that Strasburger probably mistook for 
swellings of the remains of the protoxylem elements (19, 444), but as 
shown above this has no connection with the growth of these elements, 
being due merely to their disposition. 
Sections taken about 5 or 6 cm. below the tip showed the canals to 
be much larger and more prominent, large cavities being visible. Th? 
disintegrated rings and spirals were noted floating off into the cavities 
of the canals, some of the remains, however, clinging to the bounding 
walls as is normally the case in Equisetum. 
A new and most significant phenomenon made its appearance here. 
As has been noted in the bud, there are wood parenchyma cells aggre- 
gated in the xylem region, and when the protoxylem elements split apart 
and become disorganised, these cells come to lie at the edges of the canal 
where persistent protoxylem cells are not present. It is these cells which 
attract our attention. They are rich in contents and exhibit the poly- 
hedral shape normal to cells of this tissue. Sooner or later, however, 
all these cells which border on the canal begin to round off at the ends 
adjacent to the cavity and show a decided swelling (Photo 4). As this 

