300 CYATHEACEAE [CH. 



in most of the condensed types, e.g. Heniitelia Jiorrida. Occasion alh' the}' 

 maybe disposed in two parallel rows on each side of the midrib, a condition 

 seen in Cyathea bnmonis, or Alsophila Williamsii Maxon. Their arrangement 

 in relation to the branching veins is then such as to suggest that the con- 

 densed form of the leaf is the result of lateral webbing of pinnae or pinnules 

 which were originally separate: this is' seen in the simple-leaved Cyathea 

 siniiata Hook, (Fig. 557). Comparison indicates that all such condensed 

 types, with sori approaching the margin, may be held as relatively late and 

 derivative. Occasionally the identity of the sorus is not strictly maintained, 

 pairs being seated together, suggesting either fission or fusion. In no case 

 are the sori of any of the Cyatheaceae actually marginal in position. 



The sorus of Alsophila is naked, having no indusium. The sporangia 

 are numerous with hairs intermixed, which are specially plentiful in A. 

 Taenitis Hook., a fact which is recognised in its old name Trichopteris Presl. 

 They are seated on a conically raised receptacle. This distinguishes it from 

 GleicJienia and Lophosoria, which however Alsophila resembles in the 

 usual orientation of the sporangia, and in the presence of the hairs. In 

 Heniitelia, which often has the receptacle considerably elongated as it is in 

 H. capensis, there is at the base a partial indusium in the form of a scale 

 "varying in size and shape and texture, often indistinct, and often very 

 deciduous" (Hooker). The genus has "the habit of Cyathea; a connecting 

 link, as it were, between the latter genus and Alsophila, consequently often 

 difficult to recognise" (Hooker). In Cyathea the receptacle is elevated, 

 globose, or elongated. The indusium is attached as a cup-like covering 

 round its base, and covers the whole sorus while young, but later it is torn 

 irregularly from the summit, its base remaining as a more or less persistent 

 cup. In these three steps we may see a natural progression from the naked 

 type of sorus found in GleicJienia and Lophosoria to the fully protected type 

 of Cyathea. The characters of the sori of the Cyatheaceae are beautifully 

 presented in Hooker's Genera Filicnni (for Cyathea, PI. ii, xxiii; Heniitelia, 

 PI. iv, xl, xlii, A ; Alsophila, PI. ix, xxi). These show in each the elongated 

 receptacle, the crowded sporangia with a high degree of regularity of their 

 orientation so that, as in Gleichenia, the distal face is directed basally, and 

 the proximal distally; but this orientation is not always strictly maintained 

 at the apex of the receptacle. 



The sporangia of all three genera are of relatively small size, as compared 

 with the larger sporangia of Lophosoria, and Gleichenia (Fig. 563). The head 

 which is borne upon a four-rowed stalk has an oblique annulus, which is a 

 complete ring encircling a relatively small distal face: in Heniitelia it 

 consists of 8 cells, as against 17 in Metaxya and over 50 in Lophosoria: the 

 ring has 26 cells in Heniitelia against 30 in ALetaxya, and 39 in Lophosoria. 

 These are clear indications of steps of simplification: and with it appears 



