On Azolla and Salvinia. £41 



invariably even to particular genera among Angiospermous 

 plants,* yet I believe it is characteristic of those plants 

 called Gymnospermous, in which the ordinarily convolute 

 carpel leaf is expanded or in which the ovulum is supposed 

 to be a direct continuation of the axis. 



The similarity contended for will scarcely be denied at 

 least to Azolla, in which it is extended even to the rela- 

 tions of the vascular fascicles with the base of the nucleus. 

 In both, as in all ovula, the nucleus is first formed, and is 

 afterwards gradually enclosed by the growth of an integu- 

 ment, at one period a mere annulus round its base.f 



I do not conceive the very early papillose state of the 

 nucleus in Salvinia to weaken the similarity. For in the 

 first place this indication of division is scarcely aboriginal, and 

 I do not consider a nucleus with a similar surface unlikely to 

 be found in a phaenogamous ovulum, in connection with a 

 plurality of embryo sacs, in which case the similarity will be 

 mainly increased. 



* Nepenthes. 



t The other instances in which a similar structure might exist among the higher 

 Acotyledones are Chara, such forms of Ferns as Deparia, some Cyatheee and 

 especially ? Hymenophyllum and Trichomanes. 



In Chara, in which there is also a similar but more constant disposition of the 

 two difform organs, the first objection presented is that the integument, with- 

 in which the nucleus becomes included, is not a continuous development from 

 round its base, but from as many points as there are subsequently spiral tubes. 

 The growths of distinct cells from the apices of these form what has been 

 considered by some the stigma. But I have not observed any thing like the usual 

 subsequent developments; the original nucleus itself appearing to become the 

 germinating body, that is the membrane enclosing the amylaceous granules. In 

 this genus the degree in which both organs represent the axis of the plant itself, 

 is carried perhaps to a greater extent than in any other. 



So far as I have yet seen there is nothing in common between the supposed 

 male of Chara, and the supposed males of these plants. But there is an analogy 

 between the twisted filaments it contains and the assumed male organs of Azolla, 

 and of many other of the higher Acotyledonous plants. 



The structure of the germinating organs, and of the growing points of the stem 

 and its branches appears to me to shew that Chara cannot be genencally separated 

 from Nitella, of which it is merely a more developed form. 



