IV—On plant-remains from the Silurian of Victoria, Australia, that extend and connect floras hitherto described

Abstract

The Alga, Pachytheca, is recorded for the first time from the Southern Hemisphere. In Zosterophyllum australianum* Lang & Cookson, the mode of branching of the vegetative axes, found associated with the fructifications, is of the same peculiar type as that of the other species, Z. myretonianum Penh. Besides recording a number of fragmentary remains still incertae sedis, there are descr. of terminal synangial fructifications, comparable to those previously found in other Silurian rocks of Victoria and known as Yarravia oblonga Lang & Cook-son, but more globular in outline. A new branch-system bearing sporangia is descr. as HEDEIA (p.146), erected for H. corymbosa (p.146) and attributed to the Psilophytales. It consists of an axis dividing into a number of branches, not all inserted at quite the same level. These may dichotomize and the resulting branchlets terminate in single sporangia of the same length; or the branches may divide more or less sympodially, so that the lower sporangia may be lateral or subterminal, while some of the terminal branchlets may even be sterile. The fructification retains a flat top owing to the lower (inner) sporangia being longer. The sporangia vary in length from 5 to 9 mm. at least and the branchings appear to be in more than one plane. For the first time there are recorded from the Silurian of Victoria axes bearing small spines, about 8 mm. long, comparable to those of Psilophyton Dawson. The axes cannot be definitely assigned to that genus; the spines were confined to the concave margins of curved branchlets.