568 PLANTS JAVANICvE RART0RES.
midrib, in which there is one only, and that terminating the single vein exactly as in Phlebodium, into which this group passes by species having the habit of Cyrtophlebium, but with fronds so narrow, that they are reduced to the lowest areolae, and consequently agree in character with Phlebodium.
An arrangement of veins and of sori analogous to Cyrto- pblebium exists in the real species of Cyclophorus or Niphobolus, none of which are natives of America : in all these the secondary veins are straight and parallel, instead of being arched ; they are also given off at an angle more or less acute from the primary parallel veins, which they connect ; and the tertiary or ultimate branches originating only on the upper side of each secondary vein are parallel with each other, more than three in number, and all of them bearing terminating sori.
An extensive and strictly natural group may be next noticed, though it cannot be considered nearly akin either to any of the preceding sections or to the principal part of that which follows.
This group or subgenus, the Lastrea of M. Bory, whose fronds are either bipinnatifid or simply pinnate, is chiefly intratropical. Its character consists in the secondary veins of the pinnate, and the only veins of the segments of the bipinnatifid fronds being perfectly simple and parallel, with one known exception reaching the margin of the segment, or in the pinnate species uniting with the corresponding vein, and each bearing a lateral sorus, generally about the middle, in some cases near the base, and in a few others proceeding from the base itself.
The closest affinity of Lastrea is not to any group of Polypodium, but to that section of Gy nanogram ma, the division of whose fronds, and the disposition of veins, are exactly similar, and in which the sori form very short lines of like origin. As the only distinction therefore consists in a difference, generally very slight, in the form of the sorus, it appears to me (and I)r. Blume has made a similar remark) that these two tribes cannot be generically sepa- rated, especially as species belonging to both agree in
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