46 



BRITISH FERNS. 



penetrate deeply in the bog, while the rhizoma spreads widely 

 and horizontally, but never- penetrates far below the surface. 



The fronds are both barren and fertile. The barren fronds 

 rise from the bog in May, the fertile ones in July : they both 

 disappear with the first frosts of winter. The frond is lanceolate 



and pinnate, the lowermost 

 pinnae are shorter than the 

 third and fourth pairs ; they 

 are attached by their stalk 

 only : about one-third of 

 the rachis is without pinnae ; 

 the pinnae are pinnatifid, the 

 pinnulae rounded, and always 

 entire : the whole plant is 

 erect, very slender, delicate, 

 and fragile ; it is of a pale 

 green colour ; in size, it varies 

 from that of the frond repre- 

 sented in the annexed cut, to 

 at least four times the size : 

 the fertile fronds are larger, 

 and of stronger growth than 

 the barren. 



The lateral veins are alter- 

 nate, they are forked almost 

 immediately on leaving the 

 midvein, and each proceeds to 

 the margin of the pinnula ; 

 each bears a circular mass of 

 thecae almost immediately after 

 the fork : the lower detached pinnula exhibits the veins and the 

 attachment of the thecae ; the upper detached pinnula shews 

 the thecae in situ on one side, and on the other the margin 

 of the pinnula (which is attenuated, paler, and convolute,) 

 covering the thecae : between the rhizoma and the pinnula, 

 shewing the veins, is a fertile pinna, seen from above; the 

 pinnulae being narrower to appearance, owing to the convolute 

 character of their margin. Each mass of seeds has, in an early 

 state of the plant, a small subreniform indusium attached on one 

 side to the vein, at the point to which the stalks of the thecae 

 are attached. This is shewn at the top of page 45. 



