No. 454-] OPHIOGLOSSACE/E AND MARSILIACE^. 765 



thallium of Ophioglossum (Mettenius — Filices Hort. Bot. Lips, 

 1856), it is extremely likely that the absence of chlorophyll is a 

 secondary condition, and that so far as the prothallium is con- 

 cerned, the Marattiacea; approach more nearly the ancestral 

 type than do the Ophioglossaceae. 



Both Jeffrey and Lang are agreed as to the essentially fern- 



, like character of the prothallium. This is shown in its apical 

 growth, strongly dorsiventral form, and especially in the repro- 

 ductive organs, which in Ophioglossum (Fig. i, A, B) resemble 

 to an extraordinary degree those of Marattia. The large multi- 

 ciliate spermatozoids are also entirely fern-like in form. When 

 to the close resemblance in the sexual organs is added the 

 marked correspondence in the development of the embryo, 

 which is very similar to that of the Marattiaceae and not m the 

 least like that of Lycopodium, the case seems a very strong one. 



There next remains to be considered the structure of the 

 adult sporophyte. In mo.st species of both Ophioglossum and 

 Botrychium the stem is a short upright rhizome about which the 

 leaves are spirally arranged. In Ophioglossnni pendulum, how- 

 ever, and in Helminthostachys the plant is dorsiventral. 

 Among the Marattiaceae both types also occur. Marattia and 

 Angiopteris are radial, Danaea is dorsiventral. Bower {loc. at.. 



