2S Toe Sexual Syftem. [Book VIII. 



produce a difengagement of the latter principle in the 

 form o,f vital air, and the two former are the confti- 

 tuent principles of oil 



M. Bonnet made a feries of experiments in order to 

 afcertain whether the fuperior or the inferior furfaces 

 of leaves have a greater fhare in performing perfpira- 

 tion. From the trials which he made, he concludes 

 that the inferior furfcce of the leaf is in general by far 

 the moil active in this refpect, though in one or two 

 tpecies of vegetables this difference was much lefs re- 

 markable. The mallow was the only vegetable the 

 leaves of which perfpired more by the upper than the 

 inferior furface. The method which he employed to 

 afcertain the comparative effect of the two furfaces was 

 to cover firft one and then the other furface with oil. 

 The leaves were then immerfed in tubes filled with 

 water, and the quantity of the perfpired matter was 

 cteafured by the length of the tube emptied in a given 

 time. The oil, by flopping up the pores, prevented 

 perfpiration from the furface to which it was applied. 

 Some large leaves of the white mulberry-tree being 

 kept fufpended on water with their upper furfaces in 

 contact with the fluid, faded in five days ; fome leaves 

 of the fame x tree, being placed in a fimilar fituation, 

 but with the inferior furface touching the water, were 

 preferved green for nearly fix months. 



The fexual fyftem has been the fafhionable fyflem 

 of botany for many years. It is well known that the 

 palm is of that clafs of vegetables which has flowers of 

 different fexes on different trees. The peafants in the 

 Levant, whether acquainted with this fact, or whether 

 directed to the practice by accident alone, have been 

 accustomed to break branches from the male palm 

 while in flower, and attach them to the fjsmale plant, 

 which they find to be conilantly productive of an abun- 

 dant 



