CH. v.] THE SAP. 173 



Macaire has slio\vn, that the chromule, or colouring 

 matter of leaves and flowers is identical, being only 

 more oxygenised in the latter. 



There are cii'cumstances, there are certain degrees 

 of nouiishment, of heat, and of light, though our 

 knowledge is too limited to assign them with arith- 

 metical precision, which have a tendency to promote 

 the developement of some vegetable organs rather 

 than others. Accordingly, as those circumstances 

 prevail, we find the pistils increased in number at 

 the expense of the stamens, as was obsen^ed by Mr. 

 Brown, in the case of the wallflower, and in the Mag- 

 nolia fuscata; and by M. Pioeper, in the Campanula 

 Rapunculoides ; or the pistils changed into stamens, 

 as was noticed by the same botanist in Euphorhia 

 palustris and Gentiana campestris ; so the petals have 

 been observed converted to calyx in the Ranunculus 

 abortivm, and the calyx into petals in Primula caly- 

 canthema ; petals changed to stamens in the black 

 currant, and in Capsella bursa pastor is ; and stamens 

 to petals in double flowers. But all the parts of a 

 flower have been observed changed into leaves : nor 

 is this matter of sui^prise, for these are the organs 

 most necessary for the well-being of a plant ; and 

 when the production of blossom fails, it is only be- 

 cause more foliage is required, for the elaboration of a 

 superabundant sap. Illustrations of these changes 

 of the floral organs into leaves have been obsen-ed 



