CH. VI.] THE FLOWER. 189 



mas rose {Helleborus ni(/er), the petals of wMch are 

 white, but which become green so soon as the seeds 

 have somewhat increased in size, and the stamens, 

 and other organs connected with fertility, have 

 fallen off. 



It is quite tme that some fiiiit ^vill not ripen if 

 the part of the branch beyond is denuded of leaves ; 

 but this only shews that those fniits cannot advance 

 when deprived of leaves as well as of calyx and 

 corolla — the only organs for elaborating the sap ; and 

 there are some flowers, as the Daphne mezereon, 

 autumn crocus, and sloe, that have their flowers per- 

 fected and- passed away before the leaves have even 

 appeared. 



That the petals perform an important part in elabo- 

 rating the sap supplied to the fruit, is further proved 

 by the flower being unable to bloom or to be fertile 

 in an atmosphere deprived of its oxygen ; and by 

 their absorbing more of that gas, and evolving more 

 carbonic acid than even a larger sur&ce of leaves of 

 the same plant. 



So essential is oxygen to the fertility of a flower, 

 that we shall find, in a futui'e chapter, that the sta- 

 mens of one plant absorb 200 times their bulk of the 

 gas at the time of impregnation ; and Saussure found 

 that double, or imfertile flowers, do not absorb so 

 much oxygen as those which are productive. The 

 following table shows the number of volumes of this 



