Bower.—Studies in the Phytogeny of the Filicales . ■ 503 
ascending stele. First a group of small protoxylem tracheides appears 
some three or four layers below the outer limit of the xylem ; opposite 
it the outer contour of the xylem projects as a rounded hump. Soon 
parenchyma cells aggregate internally to the protoxylem ; the outer 
xylem then projects still more, and a loop of xylem with the protoxylem 
lying centrally within it is formed (Figs. 10, 12). This body of tissue 
continues to move outwards, some of the internally-lying tracheides 
following it, while laterally a constriction is formed, equally as a rule 
on both sides. As it deepens, the leaf-trace becomes gradually shut off 
from the stele by the intruding phloem and sheaths. On the separation 
of its xylem from that of the stele, it consists of an oval tract of tissue, 
enclosing within a complete ring of metaxylem a parenchymatous island, 
and on the peripheral limit of this lies the protoxylem, which has mean¬ 
while divided into two groups (Fig. 11). Subsequently the trace becomes 
completely abstricted from the stele. It very soon opens out by separation 
of the metaxylem in a median plane, the lateral portions withdrawing, till 
the whole leaf-trace takes the form of a crescent, as in the cases of Matonia 
and Dipteris conjtigata ; the differences are that the leaf-trace is here 
narrower, and the protoxylem groups are only two in number, while the 
margins of the xylem are less strongly curved ; there is also an enlargement 
of the xylem in the median plane. But this condition is only maintained 
for a very short distance. A median constriction soon appears (Fig. 13), 
and the xylem divides through the median enlargement above noted. The 
whole leaf-trace finally divides into two equal halves, each with its own proto¬ 
xylem (Fig. 14), and in this state it passes out into the base of the petiole. 
In the mere fact that the leaf-trace is at first undivided, Cheiropteris corre¬ 
sponds to Gleichenia , Matonia , and Dipteris conjugata. In its origination 
from a protostele it compares with all the simpler Gleichenias, and differs 
from Matonia and Dipteris , except in their seedling stage. It has been 
shown by Tansley and Miss Lulham (Ann. of Bot., vol. xix, p. 496) that 
the young seedling of Matonia has a protostelic axis. The same has been 
shown to be the case of Dipteris Lobbiana , by Miss de Bruyn (Ann. of Bot., 
vol. xxv, p. >] 6 i). The young plants of D. conjugata were also examined 
by her, but the material did not suffice for demonstration of the earliest 
phases. This deficiency has, however, been supplied by young plants of 
that species collected by Professor Lang, on the Malay Peninsula, and the 
section seen in Fig. 15 shows the protostele, from which a leaf-trace is just 
passing off. It may be taken then as usual for Matonia and Dipteris that 
the axis is at first protostelic, and that it passes through a ‘ Lindsay a stage 1 
to solenostely of a more or less complicated type. Thus it is only with the 
youngest stages of these Ferns that the mature condition of Cheiropleuria 
can be compared. It has retained throughout its life the primitive state of 
Gleichenia. 
L J 
