XXXVII] ODONTOSORIA 29 



of these Ferns to other Davalhoid genera, but such difficulties are best resolved 

 by maintaining the species of Odontosoria as constituting a substantive genus 

 under Presl's old name. As representative types may be taken O. retusa 

 (Cav.) J. Sm., frequent in cultivation, of robust habit, and with leaves of 

 limited growth : O. aculeata (L.) J. Sm,, the Bramble Fern (Vol. I, Fig. 44), 

 and its ally or possibly variety, O. fumarioides (Sw.) J. Sm., both of which 

 have unlimited apical growth of their straggling and climbing leaves. They 

 were included in Stenoloma Fee, or Lindsayopsis Kuhn (Fig. 595, G). 



The species of Odontosoria are mostly rhizomatous with highly divided 

 leaves, the segments being triangular-wedge-shaped, with free veins diverging 

 like a fan. The dermal appendages are paleae of varying width: in 

 O. fitinarioides they are continued upwards into a single hair-like row of 

 cells (Gwynne-Vaughan, Ann. Bot. 1916, p. 502). Anatomically the genus 

 shows fluctuations between full solenostely and the Lindsaya-stditQ. The 

 relatively robust rhizome of O. retusa is included in Gwynne-Vaughan's 

 list of typical solenosteles {Ann. Bot. xvil, 1903, p. 691; G.-V., slides 977- 

 9S6). Its undivided leaf-trace is like that oi Microlepia, and the pinna-traces 

 are marginal; but O. aculeata (G.-V., slides 866-880) has a structure like 

 that of Tapeinidium (Fig. 594, B'). There is in fact an incomplete solenostely 

 with a sclerotic core filling a deep pocket (Gwynne-Vaughan, Ann. Bot. XVII, 

 p. 7 1 2). In O. fumarioides, which is sometimes held as a variety of O. aculeata, 

 Gwynne-Vaughan found a well-defined solenostele {Ann. Bot. xxx, p. 502). 

 On the other hand, he describes a Lindsay a-'sX.xv\c\.\xx& for O. chinensis (L.) 

 J. Sm. (G.-V., slides 914-929), and for O. clavata L. (G.-V., slides 931-932). 

 Thus the genus fluctuates between solenostely and the Lindsaya-ty^e of 

 stele. Possibly size may be a determining factor, and it is worthy of note 

 that Plumier describes the caudex of O. aculeata as no thicker than a writing 

 pen {Sp. Fil. i, p. 191), while Gwynne-Vaughan notes those of O . fumarioides 

 as fairly stout {I.e. p. 502). In accordance with their climbing habit the 

 petiolar strand in the Bramble Ferns is condensed in a manner parallel 

 with that of Lygodium or Gleiehenia. This has already been discussed and 

 illustrated in Vol. I, p. 171 (Fig. 165). 



The highly branched leaves bear deltoid pinnules with forked venation, 

 and the sori are marginal. They appear fused laterally along the width of 

 the pinnule, and are protected by upper and lower indusial flaps. A vascular 

 commissure traverses the marginal receptacle, connecting the vein-endings. 

 The development of this coenosorus has been traced in O. retusa (Studies III, 

 p. 459). First the margin of the pinnule becomes flattened (Fig. 598, A), 

 while the segmentation and localised growth form projecting angles which 

 are the upper and lower indusia (Fig. 598, B). The first sporangia appear 

 about the middle of the flattened receptacle that lies between them : others 

 appear laterally, but mostly on the adaxial side of those first formed. Thus 



