140 Dr. Meyen's Researches in Physiological Botany. 



common lettuce was taken and placed with its roots in water. 

 The result of this experiment agreed with Macaire's, i. e. a por- 

 tion of the lacteous sap was found in the water, the appearance 

 of which however M. Braconnot correctly refers to the tearing of 

 the fine rootlets. Some plants of Euphorbia Peplus which grew 

 in water, imparted to it no taste, and it remained colourless : 

 moreover the soluble substances in moulds in which Euphor- 

 bia Brioni, Asclepias incarnata, and Papaver somniferum had 

 been grown, were examined, but the results were not favour- 

 able to Macaire's conclusions. Finally, Macaire's experiment 

 with " Mercurialis annua" was repeated. One half of the 

 roots of this plant was placed in a weak solution of acetate of 

 lead, and the other half in pure water. In the end, the water 

 contained some of the lead salt which had been given to the 

 roots in the other vessel. This is, however, explained by Bra- 

 connot as the simple effect of capillary attraction in the roots, 

 an explanation to which I cannot assent ; it is by no means 

 necessary to seek for such a one, for we can explain the phe- 

 nomenon much more simply without having recourse to Ma- 

 caire's views, according to which plants have the power of 

 excreting substances injurious to them by means of their 

 roots. 



In last year's Report notice was taken of M. Payen's re- 

 searches on the chemical composition of the woody substances; 

 but they were only published with additions in the begin- 

 ning of the present year*. M. Dumas gave an excessively 

 favourable report of this research to the Academy t ; however, 

 many of the discoveries contained therein had already been 

 published in Germany, &c, as was shown in the former Re- 

 port. 



It is now several years since the newer microscopes have 

 shown that the original stratum or layer of cellular membrane 

 exhibits characters different from those of the secondary lay- 

 ers : indeed the chemical difference of these parts was proved 

 by the observations of Schleiden, and this fact has been con- 

 firmed and extended by M. Payen. The first series of ulti- 

 mate analyses was made with quite tender cellular tissue, 

 which was viewed as the primitive layers of the woody cells ; 

 for this purpose were used the ova of almonds, cucumber sap, 

 the tender cellular tissue of cucumbers, pith of elder, pith of 

 JEschynomene paludosa, cotton and " root-spongioles," (Wur- 

 zelschw'dmmchen) : by this is probably meant the small extre- 

 mities of roots ; for I have long since proved that these " spon- 



* Annales des Sciences Naturelles, 1839. Part. Botan. i. pp. 21—31. 

 f Ibid, pp.28— 31. 



