36 BRITISH FERNS. 



plants may be distinguished from each other, I must add that I 

 consider the extreme difference between dentata and angustata is 

 lost sight of when an intermediate series, running through the 

 original fragile, is carefully examined ; and further, that regia no 

 where exists in a native habitat in this country, and is not there- 

 fore to be considered as connected with the inquiry : having said 

 this, I shall make no attempt to enforce my opinions, but leave 

 the judicious botanist to form his ovsn. 



The lateral veins are alternate, and each is usually divided 

 into three or four branches, one extending to every serrature in 

 each lobe of the pinnula. The lower detached figure in page SS 

 represents a pinnula, showing the veins and points of the attach- 

 ment of the thecse ; the figure immediately above it represents 

 a lobe of the same pinnula ; almost every vein bears a mass of 

 thecse near its extremity, the mass is circular, and is covered 

 by a loose white membranous indusium, which is attached on 

 one side only, beneath the thecge ; its margin, at the farthest 

 extremity from its attachment, is striated, and becomes split into 

 capillary segments, or sometimes torn in a ragged manner, and 

 at length entirely disappears : the masses of thecse rapidly 

 increase in size, at last becoming confluent (see page 32), where 

 the apex of a frond with confluent masses is represented to the 

 left of the cut. In cultivation I have observed that sometimes 

 from the plant receiving a check from exposure or improper 

 treatment, the masses remain of small size, and covered with the 

 indusium, even after the frond has withered. 



This fern, in the wild parts of Scotland, Wales, and 

 Ireland, is particularly fond of bridges, where it establishes 

 itself in the interstices of the stones. 



