6o VASCULAR CRYPTOGAMS 



tissue is sometimes furnished with air-cavities and gum-passages, usually 

 in connection with the ' vascular ' bundle. In some of the heterophyllous 

 species these occur only in the sporangiferous or fertile leaves. In 

 Phylloglossum the leaves all spring from the base of the scape (see fig. 

 38) ; they are narrow and subulate, about half an inch in length, and pene- 

 trated by a single ' vascular ' bundle. They are colourless in their basal 

 half, green in their apical half, and have stomates only in the green part. 

 In a large number of species of Lycopodium all the leaves serve the 

 purpose of nutrition only, and the sporanges are borne in the axils of 

 ordinary leaves. But in the remaining species of Lycopodium, and in 

 Phylloglossum, the leaves which subtend the sporanges are greatly 

 modified, being of a membranous texture and colourless. In these 

 species the sporanges with their subtending leaves are usually collected 

 into spike-like ' inflorescences,' which may be short, erect, bifurcate 

 branches, as in L. clavatum, or an elongated naked scape, as in 

 Phylloglossum. 



The sporanges of Lycopodium are seated each on the base of a leaf 

 which has frequently undergone more or less metamorphosis (see 

 fig. 37, B) ; by displacement they may subsequently become axillary. 

 They are kidney-shaped, and are attached at their broader side by a 

 short thick pedicel. They are unilocular, and dehisce by a fissure across 

 the apex in the longest diameter. In all the Lycopodiacese the outer 

 walls of the epidermal cells of the sporange are composed of pure cellu- 

 lose, while the inner and side walls are lignified. Dehiscence takes 

 place by the outer face of these cells contracting more than their inner 

 face in dry air. The Small and numerous spores are sphero-cubical, the 

 exospore being marked in a variety of ways. On germinating the exo- 

 spore splits by three fissures which meet in a point at the apex of the 

 spore, the endospore projecting between the three valves thus formed. 

 The sporange originates as a prominence from a group of superficial cells 

 at the base of the leaf The original cells from which it is formed are 

 few in number ; the central one of these gives rise to the archespore. 

 The wall of the sporange ultimately consists of from two to four layers 

 of cells ; the innermost of these forms the layer of tapetal cells. The 

 mother-cells of the spores become separated from one another, and 

 invest themselves with very thick cell-walls ; from each is developed 

 four spores, and the exospore becomes elevated into warts, spines, &c., 

 before the walls of the mother-cells have become absorbed. In Phyllo- 

 glossum the sporanges are also unilocular, and are placed in the axil 

 of short triangular apiculate metamorphosed leaves ; and a large number 

 are collected into a spike-like ' fructification ' at the extremity of a naked 

 scape. They dehisce by a vertical longitudinal fissure. The spores 



