608 



giving precise limits to groups founded on these characters, and had 

 consequently returned to the old although unsatisfactory characters 

 derived from the fructification. Mr. Smith had, however, recently 

 ventured on the employment of the characters of the rhizome for the 

 formation of a dichotomous division of ferns, as already indicated on 

 the wrapper of the ' Phytologist.' He (Mr, Newman) entertained 

 grave doubts whether a dichotomous division could be made with suf- 

 ficient precision to include all the genera. The idea, which had for- 

 merly occurred to him, and which he found preserved in MS., was to 

 make a quadruple division of the ferns. 



1. Those in which the rhizome was of great endurance, of compa- 



ratively slow growth, and capable of producing single fronds 

 from any part of its surface, except the extreme point of 

 increase. These fronds were aljvays articulated at the base, 

 falling off when mature, and leaving a cicatrix like that left on 

 the twig of an Exogen when the leaf has fallen. Hence the 

 frond is a true leaf. Familiar examples : — Polypodium vul- 

 gare and Davallia canariensis. This group is in all probabi- 

 lity identical with Mr. Smith's Eremobrya. 



2. Those in which the rhizome is of less endurance, of somewhat 



more rapid growth, and in which the fronds, although widely 

 separated and distinct, as in the preceding, are, nevertheless, 

 without any basal or other articulation, and therefore do not 

 fall like the leaves of Exogens ; but their bases remain iden- 

 tical with the rhizome. Familiar examples are afforded by 

 all the Hymenophyllese, Pteris aquilina, Lastrea Thelypteris, 

 Polypodium Phegopteris, P. Robertianum, P. Dryoplcris, 

 and P. montanum. Adopting Mr. Smith's termination, Mr. 

 Newman proposed to call this group Chorismobrya. 



3. Those in which the trunk was rather a corm than a rhizome, 



which was erect or suberect, which was of great endurance 

 but of extremely slow growth, which produced fronds only 

 from its point of increase, and in which each successive frond 

 originated in the base of its predecessor, these bases being 

 exarticulated and identified with the corn), or trunk. Ex- 

 amples : — Filix-mas and Filix-foemina. To this group Mr. 

 Newman proposed to restrict Mr. Smith's very appropriate 

 name of Desmobrya. 



4. Those in which the corm, or trunk, was succulent, the frond one 



only on each corm, and its vernation straight. This group, 

 corresponding with the Ophioglossacca) of Robert IJiovvn, is 



