FILICINEJE. 



415 



Among the Forms of Tissue of the Ophioglossaceae, the prevailing one is parenchy- 

 matous fundamental tissue ; there is no sclerenchyma. It consists, especially in the leaf- 

 stalk, of long, almost cylindrical, thin-walled succulent cells with straight septa and large 

 intercellular spaces; in the lamina the latter are, in O. 'vulgatum, very large, and the tissue 

 spongy. In O. 'vulgatum and B. Lunaria, the epidermal tissue nowhere possesses special 

 hypodermal layers; a well developed epidermis with numerous stomata on the upper and 

 under side of the leaves immediately covers the outer layers of the fundamental tissue : 

 at the periphery of the stem layers of cork are formed. The fibro-vascular bundles of O. 

 'vulgatum form, according to Hofmeister, a hollow cylindrical network in the stem, on 

 which the leaves are arranged spirally, with a f phyllotaxis ; each of the meshes of this 

 network corresponds to a leaf, and gives off to it the foliar bundles from its superior angle : 

 the lower end of each foliar bundle terminates in a root. The leaf-stalk is penetrated by 

 from 5 to 8 slender fibro-vascular bundles, which, in transverse section, are arranged in a 

 circle, and between which the fundamental tissue forms wide lacunae. Each of these 

 bundles has on its axial side a strong fascicle of narrow reticulately thickened vessels, a 

 broad fascicle of soft bast (phloem) lying on their peripheral side. In the sterile lamina 

 the slender bundles branch copiously and anastomose into a network ; they run into the 

 mesophyll which contains chlorophyll, without forming projecting veins. The slender 

 stem of B. Lunaria has the same structure as that of Ophicglossum ; its vascular bundles 

 appear to be only the lower ends of the foliar bundles (Fig, 289), which are arranged in a 

 circle in the stem and form a hollow fibro-vascular cylinder consisting of numerous 

 xylem-bundles surrounded by a common investment of phloem. In each leaf-stalk, 

 which has a conical cavity below obliterated above, arise two broad ligulate bundles, 

 which split above, below where the leaf divides into the fertile and sterile laminae, into 

 four narrower bundles. Each of these latter consists of a broad axial fascicle of tra- 

 cheides thickened in a scalariform or reticulated manner, which is enveloped by a thick 

 layer of phloem. This layer shows an inner stratum of narrow cambiform cells, while 

 the outside is formed of soft thick-walled bast-like prosenchyma (as in Pteris and other 

 Ferns). In the lobes of the sterile lamina the bundles repeatedly split dichotomously, and 

 run through the mesophyll without forming projecting veins. 



The ground-tissue either forms no sheath round the fibro-vascular bundles of the 

 leaves {Ophioglossum) or it forms a sheath consisting of collenchyma {Botrychium) ; the 

 usual bundle-sheath of cells with sinuous walls appears to be wanting. According to 

 Russow, the fibro-vascular cylinder formed in the stem of Botrychium by the lower 

 portions of the foliar bundles is surrounded by a sheath of this kind (Plerome-sheath). 

 He also believes that the fibro-vascular bundles in the stem of Botrychium undergo a 

 slight subsequent growth in thickness. In the petiole of Ophioglossum I find, as Russow 

 describes, that the thin fibro-vascular bundles have collateral phloem and xylem and that 

 the central xylem of Botrychium is surrounded on all sides by phloem. 



[According to Russow, a formation of cork takes place at the surface of the rhizome 

 of Ophioglosseae ; in this, so far as is known at present, they are unique among Vascular 

 Cryptogams.] 



Habit and Mode of Life. The number of leaves which appear each year is small, and 

 constant in the species; thus O. 'vulgatum and B. Lunaria unfold only a single leaf 

 annually, B. rutcefolium two, a sterile and a fertile one ; O. pedunculosum from 2 to 4 

 (Mettenius). The extremely slow development of the leaves is remarkable; in B. 

 Lunaria each leaf requires four years, of which the three first are passed underground ; 

 in the second year the two branches (the sterile and fertile laminae) are formed, and 

 further developed in the third; in the fourth year they for the first time rise above 

 ground (Fig. 289), the process reminding one of the slow formation of the leaves of 

 Pteris aquilina ; the same occurs in O. 'vulgatum. In both genera the formation of the 

 sporangia begins a full year before they ripen. 



Vegetati've Reproduction takes place in Ophioglossum by means of adventitious buds from 

 the roots. O. pedunculosum is so far monocarpous that, after the production of fertile 



