516 TRANSACTIONS OF THE CANADIAN INSTITUTE. [Vou. VIII. 
secondary roots, the base of the stem, and of the bases of the lower leaves 
(Figs. 3 and 5). It is closely restricted to the cortex, not penetrating at 
any time even into the endodermis. ‘The mycelium consists of rather 
coarse (5-7) filamentous, branched, infrequently-septated hyphe; it 
forms loose elongated coils or bundles often in contact with the enlarged 
and apparently well-nourished nuclei of the host cells; here and there a 
hypha passes from one cell to another, and oceasionally the ends of some 
of the hyphe have the form of much swollen vesicles. So far as could be 
observed, the vigour of the ferns was in no wayimpaired by this association ; 
in fact, the presence of the fungus was wholly unsuspected until microtome 
sections of the seedlings had been examined. 
The details of the development of the stem are somewhat variable 
so that a generalized account will be given followed by a description of the 
sequence of events in several individual specimens. 
A short distance above the transitional region between root and 
stem, at about the level of the foot and on the side of the stem opposite it, 
the first leaf trace comes away. Frequently a little farther up and at 
about right angles to the plane of the cotyledon the first root takes its 
origin. ‘The earliest leaf-traces to the number of from five to eight alter- 
nate on the stem according to a % system of phyllotaxy thus exhibiting a 
bilateral symmetry that seems to be characteristic of all fern seedlings. 
This is followed by a more or less regular 34 system which may prevail 
until fifteen or twenty additional leaves have formed. ‘The roots occur 
with a regularity almost equal to that of the leaves. The roots arise 
singly, one for each leaf, at about the level at which the leaf-trace separates 
from the cauline stele, and about 90° around the stem from the correspond- 
ing leaf. ‘Thus if the points of origin of leaves and roots were plotted on a 
spiral there Would be a regular alternation of the two. In Osmunda cinna- 
momea one root for each leaf is also characteristic of the adult plant, and not 
two as is the case for O. regalis and O. claytoniana. It is attached 
much nearer to the leaf-trace in the adult than in the seedling, often in 
part to its base. 
The departure of the first few leaf-traces causes no other impression 
on the xylem of the cauline protostele than a temporary diminution of its 
tracheids (Fig. 1). But flattenings and bays above the points of separa- 
tion of the leaf-traces may occur anywhere from the third to the eighth 
node (Fig. 2). Even an ephemeral pith may be formed by the xylem 
closing up the mouth of one of these bays (Fig. 3). 
Following the restoration of the protostele with its central core of 
tracheids there is a repetition of the flattening of the xylem above the leaf- 
