Stem Anatomy and Phyllotaxis in Ophioglossum petiolatum

Abstract

Besides Ophioglossum petiolatum Hooker, subg. Ophioglossum includes approximately 20 other species. All are characterized by a radially erect, underground stem which bears a simple, oval or lanceolate leaf blade at the base of which arises a sporangia-bearing segment (Campbell, 1911, p. 86; Claussen, 1938, pp. 111-112, 1954). Stem anatomy of only seven species has been described: 0. vulgatum (Rostowzew, 1891; Vasisht, 1927), 0. moluccanum (Campbell, 1911), 0. aitchisonii (Vasisht, 1927), 0. fibrosum (Maheshwari & Singh, 1934), 0. littorale (Nozu, 1956), 0. lusitanicum (Gewirtz & Fahn, 1960), and 0. reticulatum (Sen, 1968). At the base of the stem is a protostele surrounded either partially or completely by phloem. Above this point pith develops, and the stele is an ectophloic siphonostele. The remainder of the stem contains a dictyostele of anastomosing collateral bundles with endarch xylem and no secondary vascular tissues. Root bundles are attached at the meristele edges. It is not known whether roots are associated consistently with leaf bases. Rostowzew found one root attached near each leaf base in 0. vulgatum, and Vasisht found the same condition in 0. aitchisonii. It seems possible that the roots of some species bear no discernible relation to the leaf bases; figure 2 of Gewirtz and Fahn may be interpreted as indicating this.