274 



BOTANY 



the sexual organs, and the early stages of the embryo, also approach the 

 eusporangiate type. 



The sporophyte shows certain analogies with both the Marattiaceae and 

 Ophioglossacese. With the latter it agrees in the character of the vascular 

 bundles of the stem, which are collateral instead of concentric as in the typical 

 Ferns. The leaves are circinately coiled as in the Marattiaceae. 



The sporangia (Fig. 241) may be borne upon the back of unaltered or but 

 slightly modified sporophylls, e.g. Todea, Leptopteris ; or special portions of 



FIG. 240. A, Osmunda Claytoniana. FIG. 241. Osmunda cinnamomea. Ripe 

 Sporophyll, natural size; sp, spo- sporangium. A, from above. B, from 



rangia. B, section of the rhizome of in front; r, annulus (X 45). 



0. regalis, showing the arrangement 

 of the vascular bundles (X 3). (JB, 

 after DE BARY.) 



the leaves may be completely covered with sporangia, as in Osmunda (Fig. 240). 

 Osmunda cinnamomea has the whole sporophyll covered with sporangia. The 

 sporangia are large, and the annulus consists of a group of thickened cells upon 

 one side. The dehiscence is longitudinal. The sporangium in its earlier stages 

 is much more massive than that of the typical Leptosporangiates, and cannot be 

 referred to a single initial cell. 



The apical growth of both stem and root is less regular than in the higher Lepto- 

 sporangiates, and in this respect also the Osmundacese suggest the Eusporangiates. 



