FRUCTIFICATION OF FERNS. 



353 



position of a circular series of fibro-vascular bundles containing 

 true woody tissue and ducts. These bundles form a kind of irre- 

 gular network, from which prolongations are given off that pass 

 into the leaf-stalks, and thence into the midrib and its late- 

 ral branches ; and it is their peculiar arrangement in the leaf- 

 stalks, which gives to the transverse section of these the fig- 

 ured marking commonly known as "King Charles in the 

 oak." A thin section, especially if somewhat oblique (Fig. 

 140), displays extremely well the peculiar character of the 



FIG. 141. 



FIG. 142. 



Leaflet of Polypodium, with sori. 



Portion of Frond of Hcemionitis, with sori. 



ducts of the Fern; which are termed " scalariform," from the 

 resemblance of the regular markings on their walls to the rungs 

 of a ladder. What is usually considered the "fructification" of 

 the Ferns, affords a most beautiful and readily prepared class of 

 opaque objects for the lowest powers of the Microscope ; nothing 

 more being necessary, than to lay a fragment of the frond that 

 bears it on its under surface, upon the glass stage-plate, or to 

 hold it in the stage-forceps, and to throw an adequate light upon 

 it by the side-condenser. It usually presents itself in the form 

 of isolated spots, termed son, as in the common Polypodium (Fig. 

 141), and in the Aspidium (Fig. 143) ; but sometimes these "sori" 

 are elongated into bands, as in the common Scolopendrum (Harts 

 tongue) : and these bands may coalesce with each other, so as 

 almost to cover the surface of the frond with a network, as in 

 Hcemiomtes (Fig. 142) ; or they may form merely a single band 

 along its borders, as in the common Pteris (brake-fern). The 

 sori are sometimes naked on the under surface of the fronds ; 



23 



