22 1 
Anatomy of the Oph i oglossaceae. /. 
fig. 3 will show the position of these, and should be compared with the 
figure in Bower’s paper. 1 The distinction of such irregular tracheides near 
the periphery of the pith from the outer primary xylem is strengthened 
when the departure of the leaf-trace is taken into account. The trace, at its 
departure, is always endarch, and the central tracheides disappear internal 
to it. But the position of the protoxylem of the nascent trace agrees with 
the distinction here drawn between outer and inner primary xylem in 
the rest of the xylem ring (cf. Phot. 16). 
The distinction of the outer and inner xylem is also brought out in the 
mode of departure of some of the earlier leaf-traces from the small rnedul- 
lated stele. The endarch leaf-trace departs from the outer xylem only, so 
that where the inner xylem is fairly represented it bridges across the gap 
left by the departing trace. This is shown in Phot, io, where a tracheide 
separates the pith of the stele (on the left) from the parenchyma adaxial to 
the small trace, the xylem of which is just about to separate. In Phot, n 
the same stele is shown a few sections higher up. The xylem of the trace 
has separated, but the pith is completely shut off from the leaf-gap in the 
outer xylem by a bridge of tracheides of the central xylem. 2 A similar case 
to Phot, io is represented in P"ig. 12, PI. XLV of Professor Bower’s paper, 
though not interpreted in the same way. Such a case as shown in Phots. 10, 
1 1 at once suggests comparison with those Osmundaceae in which the leaf- 
trace ‘ pocket ’ is shut off from the pith by the inner tracheides of the 
xylem, and it is possible to interpret the appearances described and discussed 
by Gwynne- Vaughan 3 in the seedlings of Osmunda on these lines. How 
close the comparison is will be clear from the four sections of another plant 
of B. Lnnaria at successively higher levels in Phots. 12-1 5. In Phot. 12 the 
xylem of a small leaf-trace is about to depart from the stem stele. The 
prominent group of parenchyma immediately within the trace is not the 
pith of the stele. This is represented by the small group of parenchyma 
more to the right. A little higher up the pith of the stem stele has 
disappeared, and the solid xylem now consists of a group of central xylem 
surrounded by peripheral xylem. The xylem of the leaf-trace, now 
separated from that of the stele, has departed in a protostelic fashion at the 
expense of the peripheral xylem only. That this interpretation is correct is 
shown by the higher section (Phot. 14), in which the pith of the stele has 
1 Annals of Botany, xxv, PI. XLV, Fig. 10. 
2 While there was nothing abnormal about this plant, which was studied in a complete series, 
the lower region of the stele, as shown in Phots. 10 and 11, presented one remarkable feature. An 
external endodermis was present in the usual position, separated by one layer of cells (the pericycle) 
from the phloem. In addition to this another cylinder of cells, with the usual endodermal markings 
on the radial walls, was present some three layers of cells further out in the cortex. Such an 
anomalous development of endodermis has a bearing on the possibility of new formation of 
endodermis in Botrychium. 
3 Loc. cit., PI. XLIV, Figs. 3, 4. 
R 
