POLYSTICHUM ANGULARE. 193 



for a simple tripinnate frond. Mr. Wollaston suggested the 

 alteration of the name, and, acting upon this ad'v-ice, I have 

 changed it to Acliurod.es, on account of its chaffyness. The 

 coloured Plate (XIV,) will therefore represent this variety, of 

 which the description on page 78 wiU be found to refer to 

 Achurodes, and not to the more common form of Tripinnatum, 

 which, although answering most of that description, is not 

 chaffy, nor has it horizontal pinna?. 



In speaking of what is called a normal form, I cannot do 

 better than quote Mr. Wollaston, whose experience on the 

 subject is very great. He considers that Suhtripinnatum is a 

 vigorous perfectly natural development ; beyond it again De- 

 compositum is the maximum of normal development. Biserratum 

 is also a vigorous normal growth, generally found near the 

 sea; and unless these three forms are in excess they are no 

 varieties. If they and the intermediate forms ranked as 

 varieties, every one picked up would be so. Of a hundred 

 plants gathered miscellaneously from the hedge no two are 

 alike; some, particularly extremes, are very unlike; but Mr. 

 Wollaston considers them all normal, although he says that it 

 requires an intimate knowledge of them to believe they are 

 not different species. 



