534 Prof. Meyen's Report of the Progress of 



experiments that substances perfectly dissolved, as for instance 

 solutions of salts, even if they are the most deadly poisons, 

 pass through the cellular tissue of plants. Towers and Un- 

 ger have also performed various experiments as to this point; 

 the first watered balsams with a solution of iron in muriatic 

 acid, and although this had entered the plant, yet even after 

 sixteen days the plant had not at all suffered. It is well known 

 that Link had previously performed similar experiments with 

 prussiate of potash and sulphate of iron, ami obtained the 

 same results ; and Treviranus has, quite without reason, 

 called in question those results of Link's experiments ; for I 

 have also succeeded with many experiments of the same kind, 

 in obtaining similar results. 



Towers placed also several balsams with the roots cut off in 

 the solution of iron, and found that they soon died in it, a re- 

 sult which was also well known from earlier experiments of 

 German botanists. Towers concludes from his experiments 

 that plants in their natural state can take up a substance 

 without injury, which under other circumstances causes death : 

 this conclusion is however too hasty, as Unger's more com- 

 plete experiments have demonstrated; these will be given 

 below. 



Thos. And. Knight* endeavours to call in question the 

 opinion that the spongioles of the root are the organs which 

 imbibe the nutritive sap from the soil, and send it forward to 

 the other parts of the plant: they were too imperfectly or- 

 ganized. Knight says that he had shown that the nutritive 

 sap in trees ascends only through the young wood or alburnum, 

 and since the spongioles of the root possess no woody fibre, it 

 must evidently be other canals, &c. which take up the sap ; 

 besides, the young wood is formed very early, long before 

 the stem and branches are developed. He is convinced that 

 portions of alburnous fibre have been erroneously supposed 

 in the spongioles of the root. (The author here probably 

 alludes to the observations of De Candolle !) It is true we 

 are still in want of an accurate demonstration of the connec- 

 tion of the spongioles of the root with those elementary organs 

 which convey the sap taken up by them onwards; but that the 

 spongioles of the root, where they are present, take up the 

 nutritive sap in the same manner as the finest fibres of the 

 root, is a fact that can no longer be called in question. 



Unger (1. c. p. 14-7) grew several plants of Lemna minor 



* Upon the supposed absorbent powers of the cellular points, or spon- 

 gioles, of the roots of trees, and other plants. Trans, of the Horticult. Soc. 

 of London, Sec. Ser. vol. ii. p. 117, [or Lond. and Edinb. Phil. Mag., vol. x. 

 p. 488.1 I was obliged to make use of the French translation, the English 

 original not having yet arrived at Berlin. 



