428 BRITISH FERNS 



LXXXI 



Revolvens {Moore) 



Mr. Jno. Wills. Somerset. 1872. 



1 ft. 6 in. 



Mr. Lucas, of Balham, was the first to notice this variety in 

 Sussex and it was then named arctatum. It has since been 

 frequently found by Mr. Wills, Mr. Moly, Mr. Padley, and Mr. 

 Wollaston in S. Devon, and in the adjoining parts of Somerset 

 and Dorset it was also found to a considerable extent and in good 

 form in Hampshire by Major Jones. Among the most marked 

 forms of this variety are a fine crispate form, found by Mr. Padley, 

 a sub-plumose form, by Mr. Moly, and one with refiexed pinnules 

 by Mr. Wills, who has also been the discoverer of some of the 

 most characteristic of the simpler forms. 



Mr. Wollaston attributes the revolvens habit (as also that of 

 reflexiim (when in excess;, and even that of flexuosum) to "the 

 natural tendency of all Ferns to protect their fructification from 

 too great an exposure to sun and rain." 



Mr. A. Leipner has supplied the following suggestions towards 

 an explanation of the flexuose habit : "In a leaf the ultimate 

 number of cells is already present whilst in a bud, and the develop- 

 ment of the leaf consists of a differentiation of these different cells 

 into the various forms and sizes as present in the parenchyme and 

 fibro-vascular bundles. 



" May not in Ferns the same hold good and the flexuose form be 

 produced by an extreme elongation of the wood cells and in the 

 rachis ? " 



Mr. Wollaston adds, "The flexuose habit both in Ferns and trees 

 must arise from the unnatural expansion or contraction of one 

 part or parcel in excess to the prejudice of the others — and that 

 this abnormal growth is caused by the extreme elongation of the 

 wood cells in the rachis." 



Mr. J. Morris writes: " I am much more disposed myself to 

 think cell division is the secret, but what is the cause of cell 

 division abnormally copious and how is it inherited? " 



Mr. E. F. Fox supports Mr. Morris's opinion. 



Whatever doubts there may be on this point, there can be no 

 doubt that it will for a long time hold its own among the first 

 dozen of the most beautiful of British Ferns. 



The Rev. H. Aubrey has suggested the idea that the flexuose 

 character is a preparatory attempt on the part of these varieties to 

 adopt the climbing habit. 



