Imperial Institute of France, 46T 



loped in the cotyledon ; that it pierces through it in growing, 

 and thai this is a character es-;ential to the plumida of all 

 the monocotyledonal plants : tiiat in the grasses, on the 

 contrary, the pluniiila is enveloped in a tunic in the form of 

 a cone distinct from the hypoblastus, and that it is this 

 tunic, which enveloping the piumula, ought to be the true 

 cotyledon ; but M. Mirbel has only shown in this small 

 cone an excrescence, resultino; from the piumula assuming 

 in the grain an increment, proportionally stronger in the 

 grasses than in the other monocotyledons. 



Arguments drawn from plants more or less resembling 

 the nelumbo have been adduced on both sides, 



M. Viirbel has shown, that there exists a great resemblance 

 between the grain? of the pepper plant and some others 

 clearly distmguishable as dicotvledons, in the structure of 

 their suckers and the grains of the nelumbo. In truth we 

 do nit see in the nelumbo, nor in the nymphaea, the annual 

 ligneous layers which distinguish the dicotyledons; butit is to 

 their loose texture, according to M. Mirbel, thai we ought 

 to ascribe this difference. 



M. Richard has produced in his favour the families of 

 the hydrocharideae and the hydropeltideae, which he thinks 

 the nelumbo and the nymphsea most resemble, and several 

 genera of which have thick hvpoblasli, in a hollow of 

 which is lodged the piumula, enveloped with % cotyledonal 

 purse, although these hypoblasti are not divided so deeply 

 as in the nelumbo. 



But at the same moment with this partial discussion 

 another ar^se : two or three years ago M. Richard, ascer- 

 taining that the division of the plants, according to the 

 number of their cotyledons or seminal lobes, is in some 

 cases obscure or even msufficient, proposed a i^ew one, 

 taken from another part of the embryo, viz. from the 

 structure and envelope of the radicle. 



In the plants commonly called dicotylcdonal, the radicle 

 or the small conical tubercle mentioned above, becomes of 

 itself, by shooting out, the root of the vegetable : in 

 others, it is only a small sac containing tubercles, which 

 become the roots. 



M. Richard denominates the plants of the first form 

 exorhizcs, and those of the second eminrhizes. 



M. Mirbel asserts that this new division is still less appli- 

 cable than the ancient; that, in truth, the radicle of the 

 frasses is conformed to this (l(.scri|4ion of the e?uiorhizes, 

 ut that in the other monocotyledons there is n(» appear- 

 ance of SIC, but a small node at the basis of th.e nascent 

 G g 2 root. 



