528 Prof. Meyen's Report of the Progress of 



position on the same ; I however consider thus much 



as certain, that the spiral fibre is not hollow." All that 

 is here said of the fibre of the spiral tubes I also assign 

 to the spiral fibres which are evident in the interior of the 

 common parenchymatous cells; for I consider these forma- 

 tions as identical. I have also in my recent work on vege- 

 table physiology* enumerated many other reasons which prove 

 in the most distinct manner that the spiral fibre is always 

 solid. At times it is thickened by a deposition of new layers 

 and exhibits at times an apparent membrification. 



On Observations respecting the System of Circulation in 

 Vegetables, 



It has been the lot of the doctrine of the peculiar system of 

 circulation in the more perfect plants in the course of the last 

 year again to sustain considerable attacks. 



Linkf endeavours to demonstrate by observations that the 

 resinous ducts of the Conifera should be enumerated, in one 

 and the same class of formations, with the milk vessels of 

 the Eupho?-biacea? and Asclepiadea? ; although not exactly si- 

 milar to one another. In young germinating Conifers Link 

 observed near the resinous passages a peculiar membrane; 

 but he himself says that in the greater and older vessels of this 

 kind they seem to disappear. I have hitherto not been able 

 to convince myself of the presence of the peculiar membrane 

 of the resinous ducts, and even the drawings of diagonal sec- 

 tions which Link J has given to these resinous ducts exhibit 

 no trace of a peculiar epidermis. Much easier is it to ob- 

 serve the origin of these resinous ducts in the young shoots of 

 Conifera?; here at least we can say with certainty that these 

 resinous passages, even in their young state, possess no pecu- 

 liar membrane; nay, even the leaves of the Coniferce (par- 

 ticularly the leaves ofPinus sylvestris) exhibit a layer of pe- 

 culiar cells which form the resinous duct, but no distinct 

 simple membrane. In the paper quoted, Link advances the 

 opinion (p. ] 32) that the resinous sap which fills those re- 

 sinous ducts in the Conifers, appears to be in motion, for the 

 substance flows out in great quantity and for a long time when 

 a branch is cut off. It would certainly be a great acquisition 

 to vegetable physiology if we could more strictly prove this 

 opinion ; but this is scarcely possible, since the vegetable parts 



[* See Bibliographical Bulletin, p. 481 of the present volume. — Edit.] 



f Element. Phil. Bot., i. p. 196. 



\ Anatomie (Vune Branche de Pinus Strobus. — Ann. des Scien.Nat., 1836. 

 i. p. 129. PI. iii. fig. 1. — Also in his Anat. Bot. Adbildungen, Tab. vii. 

 fig. 1 and 5. 



