THE BUCKLER FERNS. 45 



This is one of the best species to study with the view of 

 understanding the fructification of Ferns ; for here the indu- 

 sium, a very important organ, is remarkably evident in 

 fronds which have about reached their full development. In 

 that state the indusium is as yet closed over the cluster of 

 spore-cases, and will be seen to consist of a lead-coloured, 

 tumid, kidney-shaped, conspicuous scale, which, at the 

 proper time, becomes elevated on one side, to allow the dis- 

 persion of the spores. This may readily be noticed by 

 watching the progress of the fronds after they have reached 

 the stage just adverted to ; or if they are gathered in that 

 state for preservation in the herbarium, they are almost- 

 certain to burst, more or less, in the process of drying, before 

 they yield up their vitality. These covers are at first little 

 white scales. 



The veins of this species are also readily seen, and each 

 pinnule will be found to have a flexuous midvein, with 

 alternate venules, which are simple or forked, or sometimes 

 three-branched in different parts of the pinnule, the three 

 branched ones, if present, occurring at the base, and the 

 unbrancliecl ones at the apex. The sori are borne on the 

 branch towards the apex of the pinnule, and form a line of 

 dots at a little distance on each side of the midvein. 



The variety incisa of our Handbook of British Ferns, named 

 Lastrea erosa, L. Filix-mas erosa, and L. ajfinis by others, 

 is a magnificent Fern, much larger than the commoner 

 form of the plant, growing four or" five feet in height, and 

 having the same general features as those already described, 

 but larger in every part ; the pinnules more elongated and 

 tapering towards the point, and more deeply cut along 

 the margin ; the branches of the venules more numerous ; 

 and the sori produced over a larger proportion of the surface 

 of the pinnule, usually reaching almost to its apex. 



The variety paleacea, by some called Borreri, is remark- 

 able for the abundant and usually golden-coloured scales 

 which clothe its stipes and rachis ; and for its blunt pin- 

 nules, and its inflexed indusium. 



The variety pumila has the pinnules changed into small 

 rounded lobes, and the fructification reduced to a single row 

 of spore-cases on each side the rib of the pinna. 



The variety cristata is a very curious and very handsome 



Slant; it has the points of the frond and of the pinnw 

 ilated into a fringe or tassel, which is a very curious trans- 

 formation, and is quite constant. There arc several otliei 

 varieties known. 



