ON MEXEllA AND SPEi'IES. b/ 



the stipes being continuous and intimately connected with 

 the portion of the stem forming the intornode between the 

 fronds, from which they cannot be separated without hicera- 

 tion. In these three modes of (jrowth — that is, whether 

 the fronds are produced in a fascicle, forming an erect or 

 decumbent axis, or in a sing-le series — the principle of at- 

 tachment is identical, and there being no articulation, as in 

 Eremobrya, the bases of the stipes are so united and become 

 indurated, forming the solid portion of tlie stem. To this 

 mode of growth 1 have given tlie term Desmohri/a, and 

 in the definitions of the genera the venation is termed 

 adherent. 



The various modifications oL' l^esmobrya I have found 

 useful as auxiliary characters in indicating natural genera, 

 but there are exceptional cases of species of Lastrea and 

 Neplirodlum, with erect fasciculate vernation, not distinguish- 

 able by the character of their I'ronds from other species of 

 the same genera with decumbent uniserial vernation ; 

 nevertheless the adoption of the vernation and tlie nature 

 of the accrescent axis as part of the definition of genera is 

 of much assistance in determining the relative affinities of 

 many genera. 



In general the ditlerence between Eremobrya and Des- 

 mobrj'a, as above described, is obvious, and there can be 

 no doubt that the two modes of growth are specially dis- 

 tinct, the plants being endowed with very difi^rent natures, 

 the vital power and tenacity of life, and power of resisting 

 drought being much stronger in Eremobrya than in Desmo- 

 brya ; and it is not a little remarkable that so far as obser- 

 vations upon cultivated plants enable me to ascertain, the 

 latter are much more freely reproduced from spores than 

 the former. It is also worthy of notice that in the 

 importation of Ferns from distant countries, those of 



