Gleicheniaceae [Gleichenia, Platyzoma (= G. microphylla)].
Sporangia form circular naked sori composed of a variable number of sporangia, usually not more than ten and frequently fewer, characterised by an obliquely horizontal and almost complete annulus ([fig. 224], I). In some species of Gleichenia (sect. Eugleichenia) the ultimate segments are very small and semicircular in form ([fig. 226], C), in others (sect. Mertensia[686]) the segments are linear ([fig. 226], D), and in many species the fronds are distinguished by the regular dichotomous branching ([fig. 225]), frequently showing an arrested rachis bud in the forks[687] protected by modified pinnules ([fig. 226], D, E). In Platyzoma the leaves are simple, reaching a length of 20–30 cm., and bear small revolute oval segments.
Fig. 224.
- A. Aneimia flexuosa.
- B. A. phyllitidis.
- C. Hymenophyllum dilatatum.
- D, E, F, G. Matonia pectinata; i, indusium.
- H. Thyrsopteris elegans.
- I. Gleichenia circinata.
(A, B, after Prantl; C, G, H, I, after Bower.)
Fig. 225. Gleichenia dicarpa. (⅓ nat. size.)
Fig. 226.