Ferns with strange Indusia 



The botanical name of the Common Prickly Shield 

 Fern is Aspidium aculeatum. Aspidium is a word made 

 from the Greek aspis, " a shield,"a reference to the shape 

 of the indusium, while aculeatum is a Latin word mean- 

 ing < furnished with thorns or prickles." The specific 

 name is, of course, due to the teeth with which the 

 pinnules of this fern are provided. 



Having exhausted all the ferns likely to be found in 

 the wood proper, we must now turn our attention to 

 the stream over which the arching trees hang their 

 foliage, forming a screen through which the sun's rays 

 pierce only with difficulty. 



Three closely related ferns we expect to meet with 

 in the vicinity of one of the many waterfalls whose 

 sides, green with mosses, are kept constantly wet by 

 the spray from the water, as it dashes over the rocks. 

 The ferns referred to are the two Filmy Ferns and the 

 Bristle Fern. So delicate and membranous, or thin, 

 are the fronds of these ferns that they cannot exist 

 under natural conditions, except in situations where 

 their fronds are being continually sprayed by falling 

 water. These three ferns differ from all other British 

 ferns in possessing indusia, either urn-shaped or split 

 into two valves, which are seated at the margins of the 

 fronds. Within these strange indusia the capsules 

 are clustered round the ends of the veins which project 

 into the indusia. In the case of the Bristle Fern the 

 veins project beyond the indusia, forming the so-called 

 bristles to which the fern owes its popular name. 

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