354 



PART IV. CLASSIFICATION. 



CLASS V. 



A. HOMOSPOROUS EUSPORANGIATJE. 



Order 1. Ophio'glossaceae. This order includes the three genera 

 Ophioglo'ssum, Botrychium, and Helminthostachys. 



SPOROPHYTE. The stem is a subterranean rhizome (except in epiphytic 

 Ophioglossums), which does not branch at all in Ophioglossum, and but 

 little in Botrychium and Helminthostachys; it is usually short and 

 erect. The rather thick and fleshy roots are unbranched in Ophio- 

 glossum, but they give rise to adventi- 

 tious buds 5 they are branched in Bo- 

 trychium and Helminthostachys, and 

 produce no buds. The leaves are de- 

 veloped close together at the apex of the 

 rhizome, and are not circinate, or only 

 slightly so, in vernation ; their growth is 

 so slow that a leaf does not appear above 

 ground until the fifth year after its first 

 development ; generally, only a single 

 leaf appears a'bove ground each year, 

 when more are developed some of them 

 are sterile. The sporophylls are remark- 

 able for their peculiar branching (see p. 

 34) ; they are petiolate, and the petiole 

 branches into two, the one bearing a 

 sterile and the other a fertile lamina (Fig. 

 212), the fertile branch being situated on 

 the ventral surface of the sterile ; the 

 sterile lamina is leafy, whilst the fertile 

 lamina consists of little more than the 

 sporangia. In Ophioglossum the sterile 

 lamina is entire, and the fertile lamina is 

 spicate with two lateral rows of sporan- 

 gia ; in Botrychium the sterile lamina is 

 pinnate, and the fertile lamina is bi- 

 pinnate with marginal sporangia. The 

 sporangia are embedded in the tissue of 

 the sporophyll in Ophioglossum, but are 

 free in Botrychium and Helminthosta- 

 chys : they are not arranged in sori ; they 

 are globose, have no annulus, but dehisce 

 into two equal valves by a transverse 

 (Ophioglossum, Botrychium) or vertical 

 (Helminthostachys) slit; the wall of the 

 sporangium consists of several laj'ers of 

 cells ; the spores are numerous and tetra- 

 hedral. 



FIG. 212. Botrychium Lv.na.ria 

 (nat. size) : w roots ; st stem ;bs 

 leaf-stalk ; x point where the leaf 

 branches ; the sterile lamina (6) 

 separating from the fertile branch 



