504 Bower.—Studies in the Phytogeny of the Filiccites. 
But though Gleichenia , Matonia , and Cheiropleuria all agree in having 
an undivided leaf-trace, that is not a constant character of the genus 
Dipteris. It is so in D. conjugata , as has been shown by Seward (Phil. 
Trans., vol. 194, p. 498, PL 47, Fig. 4). But already Miss de Bruyn 
has observed that in the young plant of D. Lobbiana the leaf-trace comes 
off as two separate strands ( 1 . c., p. 769, PI. 57, Figs. 9-12). In mature 
plants it may be more complex still, and Text-figs. 6 , a-f show by a suc¬ 
cession of sections from below upwards how the trace arises. In a, the 
solenostele is about to open to form the foliar gap; b shows how, after 
opening, the margins are deflected outwards, while c shows how two 
strands have separated from the stele, and one of them has already divided ; 
Text-figs. 6 , a-f. Successive transverse sections, from below upwards, showing the separation 
of the leaf-trace from the solenostele in Dipteris Lobbiana. x 3. 
in d and e, both have divided, and the leaf-trace consists of four strands, in 
which state it passes out into the petiole: very shortly the solenostele again 
closes, as shown in f. 
These facts are here adduced because they have an interesting relation 
to what is seen in Cheiropleuria on the one hand, and in Platycerium on the 
other. In the former the leaf-trace comes off, it is true, as a single strand ; 
but it divides almost at once, in fact before it has traversed the cortex of 
the axis. In this respect it is in advance of the condition seen in Gleichenia , 
Matonia , and Dipteris conjugata. But Dipteris Lobbiana is again more 
advanced, since the trace originates as two separate strands, which divide 
again before the trace leaves the cortex of the axis. On the other hand, in 
the young plant of Platycerium Miss Allison has shown that the leaf-trace 
arises as two strands; but in the case of the mature leaf it is much more 
complex, consisting from the first, it may be, of a large number of separate 
strands (compare Text-fig. 9, below, p. 508). Thus in the matter of 
