■^(S2 VASCULAR CRYPTOGAMS. 



prolongation of the epidermis provided v/ith stomata and covering the whole of the 

 fertile branch of the leaf. At the places where the lateral transverse line of de- 

 hiscence subsequently appears in each sporangium, these epidermal cells are elon- 

 gated radially, and the whole layer exhibits an indentation at first scarcely per- 

 ceptible. The spherical cavities which contain the masses of spores are imbedded 

 in the tissue of the organ, and are therefore entirely surrounded by its parenchyma ; 

 this is found also in several layers on the outer side w^here the transverse fissure 

 subsequently arises. The middle part of the parenchyma is penetrated by three 

 fibro-vascular bundles which anastomose with one another into long meshes, and 

 send out a bundle transversely between each pair of sporangial cavities. The 

 course of development is the same in Botrychium, if the separate sporangiferous 

 branches of the panicle are compared with the spike of Ophioglossum. The 

 sporangia are similarly placed on them in two rows and alternate ; only they project 

 further because the tissue between each pair of sporangia is but slightly developed. 

 In specimens of both genera preserved in spirits the young spores still connected 

 together in fours, are found imbedded in a colourless, granular, coagulated mass 

 of jelly, which in the living plant clearly corresponds to the fluid in which the 

 spores of other Vascular Cryptogams float before they are ripe. The spores are 

 tetrahedral ; in Botrychium they are provided, even in a very early state, with knob- 

 like projections on the cuticularised exospore. 



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

 matous fundamental tissue. 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. Lmiaria, 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. The fibro- 

 vascular bundles of 0. njulgatum form, according to Hofmeister, a hollow cylindrical 

 network in the stem, on w hich the leaves are arranged spirally, with a § phyllotaxis ; 

 each of the meshes of this network corresponds to a leaf, and gives off to it the foliar 

 bundles from their superior angle. , The whole of the tissue which fills up the meshes of 

 the network is frequently transformed into scalariform vessels, so that considerable 

 lengths of the stem then form a closed hollow cyhnder; this sometimes occurs on 

 one side only. 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 presents 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 wiiich 

 contains chlorophyll, without forming projecting veins. The slender stem of B. Lw 

 naria has the same structure as that of Ophioglossum ; its vascular bundles appear to 

 be only the lower ends of the foliar bundles (Fig. 283). In each leaf-stalk, which 

 has a conical hollow 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 

 tracheides 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 split repeatedly dicho- 

 tomously, and run through the mesophyll without forming projecting veins. 



