6/4 MICROSCOPIC STRUCTURE OF HIGHER CRYPTOGAMS 







species, being almost spherical, with a slightly convex lid, without 

 beak or point, and showing no trace of a peristome ; and the spores 

 it contains are produced in groups of four (as in mosses) around a 

 hemispherical ' columel.' Besides the ordinary spores, however, 

 the Sphaynacece sometimes develop a smaller kind, the ' microspores,' 

 formed by a further division of the mother-cells ; the significance of 

 these is unknown. 1 The ordinary spores, when germinating, do not 

 produce the branched confervoid filament of true mosses, but if 

 growing on wet peat evolve themselves into a lobed foliaceous ' pro- 

 thallium,' resembling the frond of liverworts; whilst if they 

 develop in water a single long filament is formed, of which the 

 lower end gives off rhizoids, while the upper enlarges into a bud, 

 from which the young plant is evolved. In either case the pro- 

 thallium and its temporary roots wither away as soon as the young- 

 plant begins to branch. From their extraordinary power of imbibing 

 and holding water, the Sphagnacece are of great importance in the 

 economy of Nature, clothing with vegetation many areas which 

 would otherwise be sterile, and serving as reservoirs for storing up 

 moisture for the use of higher forms of vegetation. 



Filices. In the general structure of Ferns we find a much nearer 

 approximation to flowering plants; but this does not extend to 

 their reproductive apparatus, which is formed upon a type essentially 

 the same as that of mosses, though evolved at a very different period 

 of life. As the tissues of which their fabrics are composed are 



essentially the same as those to be de- 

 scribed in the next chapter, it will not 

 be requisite here to dwell upon them. 

 The stem (where it exists) is for the 

 most part made up of cellular par- 

 enchyme, which is separated into a 

 cortical and a medullary portion by the 

 interposition of a circular series of 

 fibro-vascular bundles containing true 

 \v< lody tissue and ducts. These bundles 

 form a kind of irregular network, from 

 which prolongations are given off that 

 pass into the leaf-stalks, and thence 

 into the midrib and its lateral branches ; 

 and it is their peculiar arrangement in 

 the leaf-stalk of the common brake which 

 gives to the transverse section the mark- 

 ing commonly known as ' King Charles 

 in the oak.' A thin section, especially if somewhat oblique (fig. i)15), 

 displays extremely well the peculiar character of the ducts of the 

 fern, which are termed xc<il<ii-if<>ri>i from the resemblance of the 

 regular markings on their walls to the rungs of a ladder. These 

 bundles of scalar! form ducts or ' tracheids ' are usually surrounded by 

 sheaths of .sr/ov-//r////y//r, tissue composed of cells the walls of which 



FIG. 515. Oblique section of foot- 

 stalk of fern leaf, showing 

 bundle of scalariform ducts. 



1 These so-called 'micro pore are iid\\ believed to be spores of a parasitic 



funiuis. En. 



