526 
Gwynne-* Vaughan.—Some Remarks on the 
earlier leaf-traces upon the stele of the stem. It would, however, be 
unnecessary to give a detailed description of particular cases, owing to the 
close similarity with those described by Faull in Osmunda cinnamomea. An 
attempt was made to put together a generalized account, but it proved to be 
very difficult and unsatisfactory because the individual sporelings exhibit 
great diversity in their structure. In order to get over this difficulty, and at 
the same time to attain both brevity and clearness, a few diagrams have been 
constructed representing median longitudinal sections of characteristic 
cases. 1 In the diagrams the leaves are all supposed to arise in two opposite 
rows, but since they are really arranged radially it must be understood that 
the diagrams do not express all the facts as seen in the series of transverse 
sections from which they were constructed. The diagrams are not genera¬ 
lized conceptions, but each one is intended to represent at a glance, and as 
faithfully as possible, the nature and sequence of the events in a particular 
sporeling. If diagrams on the same plan be made from Professor Faull’s 
descriptions, comparison with his results is greatly facilitated. 
In every sporeling the first two leaf-traces departed in a perfectly 
protostelic manner, i.e. without leaving any depression in the xylem of the 
stem (PI. XLIV, Figs, i and 2). The third leaf is nearly always proto¬ 
stelic, the fourth very often, and sometimes even the fifth (cf. the diagrams). 
Sooner or later, and sometimes as early as at the third leaf, the parenchyma 
of the xylem-sheath encroaches upon the xylem of the stem in the axil of 
the departing leaf-trace. In this way a groove or bay of parenchyma is 
formed which is prolonged downwards below the level of the departure to 
form a pocket (Fig. 3). The first parenchyma to appear in the solid xylem 
of the stem is often due to the formation of such a pocket (Diagrams 1 and 2). 
Just as often, however, the first parenchyma to appear is a true pith quite 
independent of the departure of the leaf-trace next above (Diagrams 3 and 4). 
It is continued past one or more leaf-trace departures without coming into 
relation with them even if they already have a pocket (Diagram 4). Cases 
also occur in which a pocket and a pith appear practically simultaneously 
(Diagram 5 and Fig. 3). 
After the fifth or sixth leaf-trace the pith opens out into the xylem- 
sheath bay above the axils of every trace forming the so-called medullary 
rays. Nevertheless, the pocket in the peripheral xylem is very often still 
formed, and is quite independent of the pith, from which it is separated by 
a flange of tracheae (Fig. 4). Sometimes this flange is short and the pocket 
opens out into the pith below the level of the leaf-trace. More often it reaches 
up to the level of the leaf-trace departure, and the pocket opens out into the 
medullary ray. Sometimes, again, it is prolonged for some distance above 
this level, and the pocket opens out into the xylem-sheath (cf. the diagrams). 
1 In the diagrams the dotted area represents phloem and pericycle, the black xylem, and the 
white parenchyma. 
