344: 



THE MICROSCOPE AND ITS REVELATIONS. 



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 

 root-fibres, while the upper enlarges into a nodule 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 Sphagna- 

 cece are of great importance in the economy of Nature; clothing with 

 vegetation many acreas which would otherwise be sterile, and serving as 

 reservoirs for storing up moisture for the use of higher forms of vegeta- 

 tion. 1 



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

 nearer approximation to Flowering plants; but this does not extend to their 

 Eeproductive 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. 



iFrc;, 227* - 



Leaflet of Polypodium, with Sori. 



Portion of Frond of Hcetnionitis, with Sori. 



those to be descibed 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 parenchyma, which is separated into a cortical and a 

 medullary portion by the interposition of a circular series of fibro-vascu- 

 lar bundles containing true Woody 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 -stalks, which 

 gives to the transverse section of these the figured marking commonly 

 known as "King Charles in the oak." A thin section, especially if 

 somewhat oblique (Fig. 226), displays extremely well the peculiar charac- 

 ter of the ducts of the Fern; which are termed 'scalariform,' from the 



1 See Dr. Braithwaite's Papers on the Sphagnacece in the " Monthly Microsco- 

 pical Journal," Vol. vi., et seq. 



