PART I. THE OPHIOGLOSSALES. 



The Ophioglossales, the "adder-tongue" ferns, include three genera (of which 

 two are practically cosmopolitan) and embrace numerous species, being sometimes 

 further divided into several subgenera; the third genus is a monotypic one, confined 

 to the tropics of the Old World. These three genera are evidently quite closely 

 related among themselves and may without hesitation be referred to a single family, 

 the Ophioglossaceae. The genus Ophioglossum includes several species of the 

 temperate regions of the whole world, and some of the species, like O. vulgatum, 

 are very widespread; the tropical species are much more numerous, but the number 

 of these is very uncertain and much confusion exists as to the limits of certain species. 

 The second genus, Botrychium, belongs mainly to the temperate regions, only a 

 small number of species occurring in the tropics, and these are principally confined 

 to the cooler mountain regions. The third genus, Helminthostachys, with a single 

 described species, H. zeylamca, is a not uncommon fern of the lowland forests of 

 the Indo-Malayan region. 



The Ophioglossaceae are for the most part quite glabrous plants, of small or 

 moderate size. The smallest species, like Botrychium simplex and some of the 

 smaller species oi Ophioglossum (e. g., 0. californicum, O. bergianiim, and some of 

 the smaller forms of O. moluccanum) may be only 5 or 6 centimeters in height. The 

 largest species of Botrychium and Helminthostachys sometimes attain a height of 

 50 centimeters or more, with ample, much-dissected leaves, while the long, ribbon- 

 like, pendent leaves of the epiphytic Ophioglossum pendulum, the giant of the family, 

 may reach a length of 1.5 meters. 



Except for two species of Ophioglossum belonging to the sections Ophioderma 

 and Cheiroglossa, the Ophioglossaceae are terrestrial plants, usually growing in soil 

 abounding in humus, and the gametophyte in all cases is a subterranean structure 

 quite destitute of chlorophyll. 



The stem is a rhizome, which is short and upright in the terrestrial species of 

 Ophioglossum and in Botrychium, but is dorsiventral in Helminthostachys and the 

 epiphytic species Ophioglossum pendulum. In most of the species of the temperate 

 regions only a single leaf is developed each year, but there are some exceptions to 

 this rule in Ophioglossum, especially in the tropical species, where there is no 

 interruption of the growth. 



The leaves are usually ample, and may be quite undivided, as in most species 

 of Ophioglossum, or they may be dichotomously divided in O. palmatum and some 

 forms of O. pendulum; or they may be much dissected, usually in a ternate fashion, 

 in Botrychium and Helminthostachys. The sporangia are sometimes very large, 

 and are borne upon characteristic spikes, or "sporangiophores," whose morpho- 

 logical nature is a matter of some controversy. The venation of the leaves is 

 reticulate in all species of Ophioglossum, but in the other genera it resembles that 

 of the typical ferns. 



With the exception of Ophioglossum (Cheiroglossa^ palmatum, the sporangio- 

 phore is normally attached to the adaxial side of the leaf, usually near the junction 

 of the lamina and petiole; but sometimes it is inserted much lower down, or it 



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