Fig. 228. Matonia pectinata. From a photograph by Mr Tansley of a group of plants in a wood on Gunong Tundok, Mount Ophir.
Hymenophyllaceae. (Hymenophyllum, Trichomanes.)
The sporangia, which are attached to a columnar receptacle or prolongation of a vein beyond the margin of the lamina, are characterised by an obliquely transverse annulus ([fig. 224], C). A cup-like indusium surrounds the lower portion of the receptacle which is two-lipped in Trichomanes and entire in Hymenophyllum ([fig. 270], C, D). These two filmy ferns have a wide distribution both in tropical and extra-tropical regions; they are represented in the British Isles by Hymenophyllum tunbrigense, H. Wilsoni, and Trichomanes radicans.
Fig. 229.
- A. Thyrsopteris elegans.
- B. Cyathea spinulosa.
- C. Davallia concinna.
- D. Dicksonia coniifolia.
- E. Alsophila excelsa.
- F, G. Dicksonia culcita.
(A, after Diels and Kunze; B, D, F, G, after Hooker; E, after Bower.)
Cyatheaceae. (Cyathea, Hemitelia, Alsophila, Dicksonia, Thyrsopteris.)
The sporangia occur in indusiate or naked sori and have an obliquely vertical and incomplete annulus ([fig. 229], E). In the great majority of cases the fronds are large and highly compound, but Cyathea sinuata Hook, a rare Ceylon species, bears simple narrow linear leaves. This family includes, with few exceptions, all the tree ferns[694]. The sori of Dicksonia are enclosed in a two-valved indusium ([fig. 229], F. G); in the species represented in [fig. 230] the fertile segments, which terminate in cup-like indusia, are characterised by the absence of a lamina and closely resemble those of Thyrsopteris ([fig. 229], A). In Cyathea the indusium has the form of a cup which is at first closed and afterwards opens at the apex ([fig. 229], B); in Hemitelia the indusium is much reduced and in Alsophila the sori are naked. Thyrsopteris is characterised by the reduced fertile pinnules bearing stalked sori in deep cups ([fig. 229], A). The appearance of this fern “is very remarkable, for the cup-shaped sori hang down from the fronds in masses, looking just like masses of millet seed[695].” The sporangia are described by Bower[696] as large and of rather peculiar form. As seen in [fig. 224], H, the annulus is continuous; it forms a twisted loop of cells which vary in shape and in the thickness of the walls. The Cyatheaceae are for the most part tropical ferns with a wide geographical range, usually in moist regions; they are, however, able to flourish under widely different temperature conditions. In Tasmania, as Diels[697] points out, tree ferns may occasionally be seen laden with snow, and on the west coast of New Zealand they overhang the edge of a glacier[698]. The monotypic genus Thyrsopteris is confined to Juan Fernandez. The Cyatheaceae no longer exist in Europe.
