226 VEGETABLE ORGANOGRAPHY. 



Section III. 



Of the Marsileacea or Rhizospermce. 



The Marsileacegg are of all Cryptogamous plants those 

 in which we most easily distinguish the sexual organs. 

 Most of them have their parts of fructification enclosed 

 in a kind of close involucrum, which appears divided 

 into several cells. We may count four in Pilularia, and 

 one in most species of Marsilea ; in each of these cells 

 or distinct cavities, we find unilocular sessile anthers, 

 which contain yellow globular pollen, and pistils also 

 sessile, formed of an oval ovary surmounted by a small 

 stigma ; these ovaries change into a monospermous inde- 

 hiscent fruit. At germination, the seed gives birth, 

 first to a radicle, and a leaf, the number of each of which 

 afterwards increases, and they finish by forming a small 

 bundle of roots and leaves. Bernard de Jussieu does 

 not hesitate to consider them as Monocotyledons, 

 near Ferns, on account of the circinate vernation of 

 their leaves. Salvinia, also presents a closed involucrum, 

 which encloses the male filiform organs surrounding a 

 solitary ovary, surmounted by a sessile stigma, and in- 

 closing several seeds. These three genera are specially 

 organized to live in water and inundated places, since 

 the organs of the two sexes are contained in the same 

 closed envelope, so that the pollen may fall imme- 

 diately upon the stigma. Azolla, which Mr. Brown 

 refers to this family, differs from the other genera in the 

 male and female flowers being contained in different 

 involucra. 



