BRITISH FERNS. 



entire; this soon becomes pushed away by the growing son, 

 and is lost. 



The variety acutum differs, prin- 

 ts- 20. cipally, in the more decidedly three- 

 cornered fronds, which, in conse- 

 quence of their shortness and 

 breadth, and the high development 

 of their basal pinnules, form a nearly 

 equilateral triangle; in the very 

 much attenuated apices of the 

 fronds and their pinnae, which are, 

 in fact, what is called caudate ; and 

 in the extreme narrowness of the 

 ultimate segments into which the 

 very much divided frond is cut, 

 these segments being narrow, linear, 

 and acute. The fronds grow a foot 

 or upwards in length, including a 

 long brown stipes. In large spe- 

 cimens the leafy portion is about 

 six inches long, and as much across 

 the base, triangular, tripinnate. The 

 lower pinnae are considerably larger 

 than the next pair, and elongately 

 triangular. The primary pinnules 

 are ovate-acuminate ; the secondary 

 pinnules lozenge-shaped, these latter 

 being cut down almost to the centre 

 into linear sharply two- to five- 

 toothed segments. The venation consists of a vein, which 

 enters each lobe of the pinnule, and branches alternately 

 into as many nearly parallel venules as there are marginal 

 teeth, one venule being directed into each tooth. The narrow 

 linear elongate sori are borne, rather close together, on these 

 venules. It is a very rare plant, having been found in a few 

 Irish counties, and in Jersey. It is met with in the North 

 of Europe, and more plentifully in the Canaries, the Azores, 

 and Madeira. 



The ordinary forms of the plant are very commonly met 

 with growing on rocks or old walls, and on hedge-banks in 

 a sandy soil. The latter situations, where they grow most 

 vigorously, are often beautifully adorned by their drooping 

 tufts. _ The extreme forms are more rare. 



This is one of the more useful evergreen Ferns for shady 

 rockwork, as it will grow with freedom if planted in sandy 



Asplenium Adianf.um-nigrum, 

 car. acutum. 



