pinnule

1 The parts of the oak fern develop with great regularity, each pinna, pinnule and lobe having another exactly opposite to it nearly always.

2 Indusium of the reflexed edges, at first reaching to the midrib, or nearly so; later opening out nearly flat; fruiting pinnules pod-like; sterile fronds broad.

3 The indusium whitish and sometimes herbaceous, formed of the reflexed margin of the lobes or of the whole pinnule.

4 Fruit in lines on the margin of the pinnules; under surface of the fronds covered with whitish powder.

5 In outline the fragile bladder fern suggests the blunt-lobed Woodsia, but in the latter the pinnæ and pinnules are usually broader and blunter, and its indusium splits into jagged lobes.

6 Very variable in the cutting of the pinnules.

7 The French pinnule is properly a sight-vane at the end of a traversing bar.

8 Sori on the edge of a pinnule terminating a vein; sporangia at the base of a long, bristle-like receptacle surrounded by a cup-shaped indusium.

9 Pinnæ sub-opposite, divergent, narrowly oblong, obtuse; base truncate, cordate or clasping, occasionally auricled; lower pinnæ often with orbicular or cordate pinnules.

10 These divisions of the pinnæ are called pinnules.

11 Var. pseudocaudàta has longer, narrower and more distant pinnules, and is a common southern form.

12 When a frond is tripínnate the last complete divisions are called ultimate pinnules or segments.

13 Small ferns with fruit-dots borne beneath the revolute margin of the pinnules, at first roundish, but soon confluent into a narrow band without indusium.

14 The leaves are gracefully arched, the pinnules rather broader than in the type, more closely arranged, and of a deep tone of rich green.

15 Pinnules on the inferior side of the pinnæ often elongated, especially the lower pair, the pinnule nearest the rachis being usually the longest, at least in the lowest pinnæ.

16 Indusium formed by the reflexed margin of the pinnules.

17 Pinnæ and pinnules ovate-oblong, densely woolly especially beneath, with slender, whitish, obscurely jointed hairs.

18 Fronds broadly triangular, ternate, one to three feet high or more, the widely spreading branches twice pinnate, the lower pinnules more or less pinnátifid.

19 Arms fork once to thrice, and bear pinnules on each or on every other brachial.

20 It is probably a fern, more minute in its pinnules than even our smallest specimens of true maidenhair.

1 小鳍

finlet

2 羽枝

barb pinnula