92 OPHIOGLOSSACEAE [ch. 



trace accord with this, while the construction of the fertile spike, unique 

 among living plants, may find its nearest correlative in the fossils of a 

 Zygopterid type. Among living plants it may have given rise by condensa- 

 tion to the spike of Ophioglossiun. Though clearly a member of the family 

 it stands as an isolated type. 



The genus Botrychiiwi, characterised by its branched spike, and its 

 seriated but separate and projecting sporangia, may be divided according 

 to the current system into three sections, of which that designated Sceptri- 

 diiivi by Lyon (1905) is probably the most primitive. This section includes 

 the teruafywi-group of species as recognised by Prantl. Their primitive 

 character is shown in the first instance by the endoscopic embryology, while 

 the foliage takes a middle position as regards the triangular form of its 

 lamina, its cutting and venation. The spike is inserted low down. The 

 section Eu-BotrycJiium includes the species grouped with Limaria, having 

 smooth leaves, oblong or deltoid, and never more than doubly pinnate. 

 They have exoscopic embryogeny. The section also includes reduced types 

 such as B. simplex. The section O sniundopteris comprises the virginianum 

 types, with relatively large leaves, some being five times pinnate, and hairy, 

 and often of thin texture. The stem has an active cambium. The embryo- 

 geny is exoscopic. These characters are held to indicate a relativel}' 

 advanced state. 



The genus Ophioglossum is commonly regarded as typical of the family, 

 and accordingly placed first (Christensen's Index, p. Iviii; Hooker's Synopsis 

 Filimm, p. 444; Engler & Prantl, Naticrl. Pflanzenfam. I, 4, p. 465; Christ's 

 Farnkraiiter, p. 362). But on grounds explained above it should be placed 

 last, as being derivative. It has been subdivided into three sections, of 

 which that designated Eu-Ophioglossiun includes O. vulgatimi, and the large 

 proportion of species characterised by a ground-growing habit, the sterile 

 blade and spike as a rule simple, and the sporangia sunken and large. The 

 stele is dilated and dictyostelic, usually without endodermis, and the leaf- 

 trace is undivided at departure. The section OpJiioderma includes the 

 epiphytic O.pendidnni together with the ground-growing species i7itermedium 

 and simplex. The first is characterised by occasional irregular branching of 

 the sterile blade and the spike, the large size of the latter and of its sporangia, 

 and particularly by the subdivision of its leaf-trace at departure. Its 

 embryogeny is exoscopic. Its mycorhizic habit leads in the allied, ground- 

 growing species to the reduced structure seen in 0. intermedium and simplex. 

 Lastly, the section Cheiroglossa includes only O.palmatum which is epiphytic 

 on rotting trees, and is characterised by frequent branching of its sterile 

 blade and fertile spikes, thus leading to a plurality of spikes. The stem is 

 distended, and the leaf-trace divided at departure. These features suggest 

 a state of advance upon the vidgattcm type. Accordingly the phyletic 



