FILICINEAE. — OPHIOGLOSSEAE. 245 



time shut up in the sporangia, and pass the winter there. The prothallium of the 

 macrospore is much reduced, ahnost to a single archegonium ; the prothalHum of the 

 microspore is reduced to one cell, as in the Salviniaceae. The fertile portion of the 

 leaf, the portion which forms the sporocarp, is a shoot from the petiole of the sterile leaf. 



B. EUSPORANGIATE FILICINEAE'. 



The two families which compose this group are especially distinguished from 

 their allies by the mode in which they form their sporangia, though they also agree 

 together in other important points. The germination is thoroughly known only in 

 the Marattiaceae ; the prothallia of the Ophioglosseae are known only as small 

 underground tubers without chlorophyll ; those of the Marattiaceae form a large 

 green thallus resembling the prothallium of other homosporous Ferns. In both 

 families the antheridia are sunk in the tissue of the prothallium (a pecuHarity which 

 they share with the rest of the homosporous Eusporangiatae, for in Equisetum also 

 the disposition of the antheridia is similar), and the neck of the archegonium also 

 scarcely reaches above the surface of the prothallium. It is highly probable that a 

 green prothallium is first formed in the Ophioglosseae as well as in the allied family, 

 and that this gives rise to the small tuber which buries itself in the ground ; at least, 

 the analogy of Gymnograjnme leptophylla points to this. The stem of the second, or 

 asexual generation, the sporophyte, is remarkable in both families for its extremely 

 small longitudinal growth, by the consequent absence of internodes and branching, 

 by the entire concealment of the surface by the insertions of the leaves, and by the 

 formation of roots in acropetal succession close behind the apex. Both families are 

 distinguished from the true Ferns by the absence or imperfect formation of bundle- 

 sheaths, and of sclerenchyma with brown walls in Ihe fundamental tissue of the 

 stem and leaves, the Ophioglossaceae being the furthest removed from them by their 

 peculiar mode of vegetation, and by the secondary growth in thickness of the stem, 

 insignificant it is true, which has been ascertained in Botrychium. 



1. OPHIOQLOSSEAE \ 



The prothallium {oophore, oophyte) is known only in Ophioglossum pedunadosum 

 and Botrychium. In both cases it is an underground body formed of parenchymatous 

 tissue and without chlorophyll, which in the former species, according to Mettenius ', 

 takes the form of a small round tuber, from which is developed a cylindrical vermiform 

 shoot growing erect under ground by an apical cell, and rarely putting forth a few 

 branches ; when the apex appears above the ground and assumes a green colour, it 

 becomes lobed and ceases to grow. The tissue of this prothallium is differentiated 



' Called by Sachs the group of Stipulatae ; but this name can hardly be maintained now that 

 we know that there are no stipules in the Ophioglosseae, and that they are sometimes wanting in 

 the Marattiaceae. 



^ Mettenius, Filices horti bot. Lipsiensis, Leipzig, 1856, p. 119.— Hofmeister, Abhandl. d. Kgl. 

 Sachs. Ges. d. Wiss. 1857, p. 657.— Russow, Vergl. Unters. Petersburg. 1872, p. 117.— HoUe, 

 Ueber d. Vegetationsorgane d. Ophioglosseen (Bot. Ztg. 1875).— Goebel, Beitr. z. vergl. Entwicklungs- 

 gesch. d. Sporangien, in Bot. Ztg. 1880 {Botrychumi) und 18S1 {Ophioglossum).- [Prantl. Beitr. z 

 Syst. d. Ophiogl. (Jahrb. Kon. Bot. Gart. Berlin, III, 1884).] 



■' A fresh examination of this species is much to be desired. 



