THE RESERVE MATERIALS OF PLANTS. 71 



are either not well ascertained or not particularly distinctive. 

 The most reliable is perhaps that with vanilin in the pre- 

 sence of hydrochloric acid. When this is made to react 

 upon a cell which contains phloroglucin in the sap, the 

 latter forms a fine precipitate of red granules which are 

 composed of a compound of vanilin and phloroglucin, known 

 as phloroglucivanilni. 



Phloroglucin appears to be often present in the plasma 

 of meristem cells rather than in the vacuole, for when chlo- 

 ride of vanilin is added to a tissue containing it the colouring 

 mainly affects the protoplasm, some of the vacuoles remaining 

 altosfether uncoloured. 



The distribution of phloroglucin, like that of tannin, 

 leaves a good deal of uncertainty as to its physiological 

 meaning. It has been investigated in recent years by 

 Waage (73), who has carefully examined representative 

 plants taken from almost all sections of the vegetable 

 kingdom. Out of 185 plants submitted to experiment 

 135 showed it to be present, but in very different quan- 

 tities. Of the 135, 51 contained a very considerable 

 quantity, 41 less but still a tolerably large amount, 

 while in 43 though present only a feeble reaction could 

 be obtained. Its distribution was to a certain extent 

 regular, for the author states that if one species contains 

 it, it is found with tolerable certainty in all the species of 

 that genus. The plants of the Polypetalae as a rule show 

 most, while the Gamopetalae and the Monocotyledons are 

 on the whole poor in it ; lower down in the scale the Vas- 

 cular Cryptogams and the Gymnosperms are charged with 

 it to a degree intermediate between the other groups. 



Examining the tissues of such plants as contain a con- 

 siderable quantity it may be found in meristems and in 

 permanent tissues. In axial organs it occurs in the 

 epidermis and later in the bark ; also in the parenchyma 

 of the cortex, and in the sclerenchyma of the tissues more 

 deeply seated. It is found sometimes in the endodermis ; 

 also in the dead cell walls of the xylem parenchyma, fibres, 

 and vessels. The medullary rays frequently contain a 

 certain quantity. It is uniformly absent from the bast 



