262 On Azolla and Salvinia. 



secondary capsules with those of Salvinia, the genus imme- 

 diately preceding it, is not noticed. 



M. Endlicher's* character is obviously derived from that 

 of Martius ; one difference being his applying the term 

 columella, (the columnula of the organum calyptratum of 

 Martius,) to the three-legged axis of this botanist ; another 

 his stating the lobes attached to it to be antheriform.f 



* Gen. PI. p. 67, No. 688. 



t In Mr. Hervey's Genera of S. African Plants, I find a character of this 

 genus taken from Kaulfuss, but it would be impossible to identify the genus 

 without the synonymy. 



The terms used in most of the characters, except those of Mr. Brown, are in 

 several instances unintelligible, as generally is the case when a name is made to 

 pass for an explanation, or when the application of a name is founded on mis- 

 taken ideas of the nature or analogies of certain parts. In the late work on 

 Genera by M. Endlicher, I find the terms indusium, calyptra, and columella, all 

 in use. And in a note, other general analogies are so extended as to refer one of 

 the organs to the type of a " flos monadelphus ovario infero." 



Now of the terms above cited, there appears to me only one, (calyptra,) 

 capable of legitimate application, but only as far as regards mechanical function. 

 The difference otherwise is very great ; for in Azolla the calyptra is nothing more 

 than what is presented by every dehiscentia circumscissa of a fruit, and is limited 

 to one only of the capsules ; while in Mosses and all calyptrate Hepaticae, it is 

 the pistillum displaced from its base at a remarkably early period. A more real 

 analogy of this part in Azolla is to be found, perhaps, in the seed of Lemnaceaa 

 during germination. 



The term indusium is applied to the capsule itself, whereas, correctly speak- 

 ing, it is only applicable to a covering of capsules of a partial or general na- 

 ture derived from the surface of the foliaceous body or frond, on which the cap- 

 sules are situated. This term indusium, which should be distinguished from 

 involucrum, is at most only applicable to Azolla. 



A columella is the remains of an originally continuous, solid, cellular tissue, 

 unaffected during the development of the spores ; it is a continuation either of 

 a partial or a special axis. It may, I believe, be justly considered analogous to 

 the connectivum of a bilocular anther, or the cellular tissue between the 

 cavities of a plurilocular anther. In Azolla it does not appear to be even solid. 



It may be seen also, that the same character gives an indusium to one, a calyp- 

 tra to the other body, while the application of the term calyptra ceases to be 

 even mechanically correct from being applied to the whole capsule. 



