538 



MARSILEACE^C. 



to particular genera among Angiospermous plants/* yet I be- 

 lieve it is characteristic of those plants called Gymnosper- 

 mous, in which the ordinarily convolute carpel leaf is expand- 

 ed or in which the ovulum is supposed to be a direct conti- 

 nuation of the axis. 



The similarity contended for will scarcely be denied at 

 least to Azolla, in which it is extended even to the relations 

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

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

 wards gradually enclosed by the growth of an integument, at 

 one period a mere annulus round its base.f 



1 do not conceive the very early papillose state of the nu- 

 cleus 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 



* 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 Cyatheae and especially ? Hymenophyllum and Trichomanes. 



In Chara, in which there is also a similar but more constant disposi- 

 tion of the two difform organs, the first objection presented is that the 

 integument, within which the nucleus beomes included, is not a conti- 

 nuous development from round its base, but from as many points a3 

 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 develop- 

 ment ; 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 car- 

 ried perhaps to a greater extent than in any other. 



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

 posed 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 Aco- 

 tyledonous 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 generically separated from Nitella, of which it is merely a mome de- 

 veloped form. 



