AZOLLA AND SALVINIA. 



559 



mella, (the columnula of the organ um calyptratum of Mar- 

 tius 5 ) to the three-legged axis of this botanist; another his 

 stating the lobes attached to it to be antheriform.* 



The genus Salvinia is said to have been first established 

 by Micheli.f He considered the papilliform hairs on the 



* 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 mistaken 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, (calyp- 

 tra,) capable of legitimate application, but only as far as regards mecha- 

 nical 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 Hepaticje, 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 Lemnaceae during ger- 

 mination. 



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

 speaking, it is only applicable to a covering of capsules of a partial or 

 general nature derived from the surface of the foliaceous body or frond, 

 on which the capsules 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 continua- 

 tion either of a partial or a special axis. It may, I believe, be justly con- 

 sidered analogous to the connectivum of a bilocular anther, or the cel- 

 lular 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 calyptra to the other body, while the application of the term calyptra 

 ceases to be even mechanically correct from being applied to the whole 

 capsule. 



f Nov. Gen. p. 107, t- 58. 



