266 PHYSIOLOGICAL BOTANY. 



of Latliyrus odoratm ; but we have never seen that the 

 radicles of these seeds sank more deeply into the mercury 

 than was caused by the pressure which the weight of the 

 seeds exerted upon the radicles, i. e. not more than three 

 millimeters." The Report concludes with the statement 

 that the phenomenon ensues according to known laws ; 

 that M. Durand has discovered that the penetration of the 

 radicles into the mercury depends upon the seeds being 

 fixed, and that when this is not the case, the seeds merely 

 penetrate as deeply as the pressure of the seed causes 

 them to do. The Report censures M. Payer for inaccu- 

 racy in the description of his experiments ; but this would 

 apply still more strongly to the account which the reporter 

 gives of his own experiments, for he makes no mention 

 of the direction of the radicles which penetrated, and yet 

 this is the main point, if it were really the pressure of the 

 seeds which forced the radicle into the mercury. More- 

 over it will appear easily explicable that the radicles 

 penetrate the mercury, when the seed is fixed, because 

 this is the only remarkable circumstance, and it is strange 

 enough, when Durand's statement is brought forward. 

 If seeds are placed in water over mercury, without being 

 fixed, they lose as much in weight as the water which 

 they displace; thus they exert less pressure upon the 

 mercury, and cannot, therefore, penetrate ; since, by 

 fixing them, the weight is entirely removed, and could 

 not, therefore, cause the roots to penetrate, there is no- 

 thing else but the force of the onward growth to make 

 the root descend, and it is remarkable that this is not 

 prevented by mercury. The experiment of Payer is very 

 remarkable ; he found that the roots of Latliyris odoralus 

 descended through several layers of mercury., in an in- 

 genious apparatus arranged for the purpose. It is also 

 remarkable, that when the radicle is withdrawn from the 

 mercury, the portion which had penetrated will not again 

 do so ; but the newly-emitted part does, an experiment 

 which excludes all mechanical explanation. The experi- 

 ments upon the penetration of the radicles of unattached 



