(58 OX GENERA AND SPECIES. 



the division Eremobrya generally arrive in good con- 

 dition, while those of Desmobrya, especially such as have 

 slender stems, are often dead or in a very enfeebled state 

 on their arrival. 



The difference in the structure and mode ot growth of 

 the species of these two divisions may be admitted to be of 

 equal importance for classification with the difference in 

 structure of Exogens and Endogens in flowering plants. 

 In all attempts to determine natural relationship on any 

 special organ or structure, exceptions are never wanting. 

 In the present case, examples of connecting* links are in a 

 few instances found between the two divisions. This is 

 particularly so with the genus Elaphoglossum, which con- 

 sists of numerous simple-fronded Ferns, and may be 

 viewed as a truly natural genus. In many of the species 

 the stipes have an evident articulation situated in some, 

 more than half an inch above its base, and in many 

 of the species it is marked by a slight swelling ; and 

 also by the part below the swelling being of a dark colour. 

 No change, however, takes place in the structure, the bun- 

 dles of vascular fibre pass uninterruptedly through the 

 apparent articulation, but they are evidently weaker at 

 that point ; for, when mature, the stipes separate there, 

 the base portion remaining attached to the developing axis, 

 which is either fasciculate or uniserial and adherent. I 

 therefore place Elaphoglossum in Desmobrya. 



Another instance of the stipes being jointed above its 

 base is characteristic of the original species of the genus 

 Woodsia, as also in species of Arthropteris ; but the base of 

 the stipes being adherent, indicates their position to be 

 in Desmobrya. Also special examples of the articulation 

 of the stipes in fasciculate vernation is exhibited by the 

 genus TricJioptens and several species of Cyatlwa ; for 



