182 W. T. GORDON 
Diplolabis, on the other hand, there was a distinct resemblance to that species (Clepsy- 
dropsis) in the early form of the petiole-trace. 
SUMMARY. 
In this paper a fern stem is described, and the evidence for referring it to Meta- 
clepsydropsis duplex (Williamson) is cited. The stem is shown to be a long, 
dichotomously branched rhizome, from which petioles and roots are only emitted at 
considerable intervals; indeed, although several inches of one stem were cut into 
transverse sections, only one petiole departure was observed, and Miss Benson followed 
another stem for nearly 2 feet without discovering any such emission. Several pieces 
of the stem were discovered. Branching of the stem is shown to be of the nature of 
a dichotomy. 
The petiole-trace is followed from the earliest stages of its differentiation from the 
stem until it departs as a separate trace. From that level it is followed through several 
series until the normal form of the WM. duplex petiole-trace is attained. The Dinewron- 
like type of the early petiole-trace is recorded. 
The pinna-trace departure is next studied, and the changes noted from the time 
the pinna-trace-bar leaves the petiole-trace until the tertiary pinne are reached. 
Several cases of abnormal traces are noted in which the xylem forms a closed ring. The 
resemblance which such an abnormal type has to what is the normal form in Clepsy- 
dropsis is commented on. 
Root-traces are also observed, and they are diarch, with a barrel-shaped xylem mass. 
The cortex is dealt with in general terms, as there is nothing of special note in its 
organisation. In the cortex of the stem and early stages of the petiole, however, there 
is no sclerenchyma present. 
One specimen of the stem is recorded which shows secondary thickening, but it is 
probably abnormal. It appears similar to Botrychioxylon. 
The species is then compared with the members of the Zygopterideze which 
resemble it. 
Metaclepsydropsis duplex (Williamson). 
1874. Rachiopteris duplex, Williamson, Phil. Trans. Roy. Soc., vol. clxiv. 
1889. Asterochlana (Clepsydropsis) duplex, Stenzel, Die Gattung Tubicaulis. 
1896. Clepsydropsis sp., Renault, Bass. howill. et perm. d’ Autun et d’Epinac. 
1909. Metaclepsydropsis duplex, P. Bertrand, Htudes sur la fronde des Zygoptéridées. 
1910. 43 Ay Seward, Fossil Plants, vol. ii. 
DIAGNOSIS. 
Stem long, dichotomously branched; xylem of stem circular in transverse section ; 
2mm. in diameter; elements in two zones. Inner zone of long, narrow, reticulately 
or scalariformly thickened tracheides, together with some conjunctive parenchyma. 
