524 TRANSACTIONS OF THE CANADIAN INSTITUTE. [Vou. VIII. 
Such are the observations on the nodal pockets of Osmunda cin- 
namomea. As to their interpretation two conclusions are suggested— 
that they are homologous with the tissues enclosed by the xylem, portions 
(usually of parenchyma only) that are enclosed by the xylem for a greater 
or a less distance; and that they owe their existence to an evolutionary 
tendency on the part of the xylem to increase in the direction of the pith. 
If such be the case, the nodal pockets are to be regarded as indications 
of ‘“‘cladosiphony’’—not primitive, but a cladosiphony secondarily pro- 
duced. 
A perfect condition of cladosiphony may rarely be observed in normal 
stems, the xylem in such cases remaining unbroken on the medullary side. 
This phenomenon is of rarer occurrence than might appear from an ex- 
amination of a single cr a few serial transverse sections, for on account of 
the obliquity and tenuity of the ray it is demonstrable only in complete 
series. The same explanation may be given as for the pockets, complete 
cladosiphony resulting from an entire closure of the inner end of the 
medullary ray. 
But the most pronounced instances of ‘‘cladosiphony’’ were found 
in plants that had been subjected for some time to adverse conditions. 
In such plants there is often a great diminution in the size of the stele, 
and it not infrequently happens that while there may be deep pockets of 
parenchyma opening outward, not a gap is formed for several nodes 
(igs. e789 To). 
These plants were collected in the neighborhood of Toronto and were 
quite readily detected by the smaller size and number of their leaves. 
They were not seedlings, for each one Was carefully traced back from the 
crown, and was found to have formerly possessed a stem of normal adult 
robustness. Just what the adverse conditions were was not determined. 
The sequence of events in the stele of one of these proved to be of 
peculiar interest, because of the discovery of an internal phloem, and 
hence will be given in some detail. 
The stele gradually diminished in diameter and the medullary rays 
narrowed. Finally the xylem remained continuous on the medullary 
side; the cylinder of xylem was relatively very thick, and the parencyhma 
pockets and external bays above the leaf traces well developed. ‘The pith 
was reduced in volume. ‘The leaf-gaps several nodes up again formed. 
This was followed by closure and an extensive sclerification of the pith. 
By degrees the outer surface of the xylem became smoother, and the 
thickness of the wall of the cylinder to diminish. Very soon isolated 
