90 Salmi.— On an Australian Specimen of Clepsydropsis. 
of the primary rachis. It is interesting to find that, so far as our present 
knowledge goes, the symmetry of the stem in the two groups is quite 
distinct. Thus in the only genera of the Dineuroideae in which the stem is 
known, viz. Diplolabis and M etaclepsydropsis (Gordon, 1911 a, b), it had the 
form of a creeping rhizome with the leaves confined to the dorsal side and 
rising perpendicularly from it. On the other hand, in the Clepsvdroideae, 
in which our knowledge of the stem is more complete, the leaves arose 
radially on all sides of the stem, which was either an upright stock (Astero- 
chlaena (Bertrand, 1911 b ), C. kirgisica (Stenzel, 1889, Fig. 38, PL IV), and 
the Australian Clepsydropsis) or, as in C. (Ank.) scandens (Stenzel, 1889; 
Scott, 1909), it scrambled among the roots on the upright stem of a 
Psaroniits. 
It appears as if the precocious bifurcation of the pinna-trace in the 
Dineuroideae (except Gyropteris ), and the consequent peculiar habit of the 
petiole in that sub-family, had something to do with the manner in which 
the basal portion of the leaf was held. One is tempted to expect that the 
stem of the remaining Dineuroideae will also be a horizontally creeping 
rhizome. 
VI. Summary. 
A description is here given of a Clepsydropsis , collected near Mt. 
Tangorin, New South Wales, in rocks possibly of Carboniferous age. It is 
specifically identical with the fossil briefly described by Mrs. Osborn in the 
Report of the British Association (Manchester meeting, 1915, p. 727). 
It is shown that in C. antiqua , Unger, also, the leaf-trace arose as 
a closed ring of xylem which became tangentially flattened, and then 
became clepsydroid as the result of a median constriction. This fact 
strongly supports the suggestion put forward in an earlier paper that the 
genera Clepsydropsis and Ankyropteris should be united, the leaf-trace 
origin in the latter genus being known to be essentially the same. 
The two groups of the Zygopterideae (Clepsydroideae and Dineu- 
roideae) were also sharply distinct in the symmetry of their stem, which, so 
far as we know, was radial in the formal group and dorsiventral in the 
latter. It is suggested that this distinction will be maintained as our know- 
ledge of the stem becomes more complete. The apparently radial symmetry 
of the basal region of the leaf in the Dineuroideae (due, as previously shown, 
to an early bifurcation of the pinna-trace) may also be related to its probably 
strictly upright position in that sub-family. The opinion has already been 
expressed in an earlier paper that this apparently radial symmetry was not 
continued into the probably more or less horizontal laminated distal portion 
of the leaf. 
Botany School, Cambridge, 
April 1, 1918. 
