Piench K'a/ional I/isiiiute. So7 



of the embryo, and which serves as a conductor to the fe- 

 cundation : that the cotyledon, as M, Jussieu supposed, is 

 a pulpy suhstance, in which the radicle and the plumula 

 are insensibly dcvelopped, and which is opened accord- 

 ing; to its length, in order to allow them to pass in such 

 a way that bv itself it performs the function of a sheathing 

 leaf. 



In general the cotyledons have the greatest analogy with 

 the leav^es ; like the latter, ihey are irritable in the sensitive 

 plant, bear hairs in the borage plant, a srland at the end in 

 plaintains, and coloured points in the herb burnet, &c.; ia 

 short, there are real leaves in the seed. If the cotyledons, 

 when there are two of them, are always opposite, even when 

 the leaves of the plant are alternate, it is because the stalk 

 cannot be developped in the seed, and the interval between 

 the two cotyledons cannot be marked. From these multi-- 

 plied connections of form and nature between the cotyle- 

 dons and the leaves, M. Mirbel concludes that the number 

 of these sa'ie cotyledons should also have its cause in some 

 circumstance relative to ihe leaves, and he thinks that the 

 monocotyledontal plants are always those v>hose leaves are 

 sheathed within each other: this is evident with respect to 

 the grasses and the li/incece, particularly if we reiltct that 

 the bulb is formed of the sheathing of the bases of all 

 the leaves; and also with respect to several other plants of 

 this branch of the vegetable kingdom. 



Passing to the formation of the wood, M . Mirbel shov\ s 

 that it is always composed of fibres dispersed here and there 

 in a cellular texture similar to the sap of the dycotyledonta, 

 but which is formed in several monocotyledonta of these 

 fibres at the circumference as well as at the centre : these last 

 have consccjuently two vegetations ; one around the outside, 

 which increases the diameter of their trunk, and the other 

 at the centre, which increases their density. He considers 

 each of the fibres ol the trunk of the monocotyledonta as if 

 it answered to an entire trunk of a dycotyledon, and shows 

 that there takes ])lace a scries of operations equally com- 

 plete as in these trunks. 



M. Mirbel has been rewarded for these ingenious labours 

 by being elected a member of the In3titute,^in the room of 

 the late M. Venlenat. 



M. Decandolle has this year conferred additional favours 



on the science of botany. lie has drawn up a memoir on 



plants with compound flowers, in which he forms a sepa- 



'■ate i'amily oi those whose flowerets have two inccjual labia, 



U a and 



