570 PLANTS JAVANICiE RARIORES.
Fohjpodium vulgare is one of the best examples of this section, which, however, comprehends species with undi- vided, pinnatifid, pinnate, bipinnate, and even decompound fronds, and these as various in texture as in division. Many species are found within the tropics ; but the section includes all the European Polypodia and most of those found in the higher latitudes of the southern hemi- sphere.
As this section includes many of the earliest described species of Polypodium, it would require, if retained entire, no subgeneric name. But in a complete analysis of the genus it ought to be divided. The strictly natural sub- divisions, however, can hardly be characterised from modifications of vascular structure alone ; and I have not yet been able to detect sufficient differences, either in the capsules or seeds, by which they may be distinguished.
That subgeneric or sectional characters may in several instances be obtained or assisted from the seeds of this Natural Order is not improbable, and in one case, namely Ceratopteris (or Teleozoma), including Parkerla in that genus, even the generic character appears chiefly to reside in the seeds, which in their unusual size and peculiar marking or striation entirely agree in all the species of the genns, while in the original species the annulus is nearly complete ; and in Parkeria, differing from the rest of the genus in no other point whatever, the ring is reduced to a few faint striae.
Tab. I. Fig. 1. A frond of Polypodium (Dipferis) Horsfieldii, of the natural size. Fig. 2. A portion of the under surface magnified, showing the arrangement of the veins and sori. Fig. 3. Another portion of the same, from which a sorus has been removed to show its insertion. Fig. 4. A sorus, more highly magnified. Fig. 5. A cap- sule before bursting. Fig. 6. A capsule after bursting. Fig. 7. Sporules.
�� �
