40 



Dr. M. J. Schleiden's Observations on 



differences existing between the membrane of various plants 

 and groups of plants inter se. Since Mohl and I have arrived 

 at this result independently, and in part by a very different 

 path, it is, in my opinion, a great presumption of its correct- 

 ness. I gladly follow the steps of Mohl, whose memoir ap- 

 peared some months earlier, as a confirmation only of a view 

 already advanced ; and would with joy always renounce in his 

 favour all claim to priority, could I thereby for ever purchase 

 an agreement of our convictions. 



Scarcely more than in expression do Mohl and I differ in 

 our views respecting the structure of the secondary deposits. 

 If he admits an arrangement of the smallest parts in the di- 

 rection of a spiral in the cases by far most frequent, and 

 if I, — believing that I frequently have actually seen this ar- 

 rangement even in cases where soon an apparent homoge- 

 neity occurs, and also as the changes produced by the expan- 

 sion of the cells prove that the connexion of the molecules, 

 in any other direction than that of the spiral, is in the 

 younger stages almost nothing, — consider myself justified in 

 speaking in all cases of a spiral striping or band, there is in 

 this, with respect to the essential point, little discrepancy. I 

 also believe that many differences of opinion, in subordi- 

 nate points, will still disappear if Mohl keeps more accurately 

 in view individual development, and especially pays more 

 attention to the momentum of the expansion of the cells 

 after the appearance of spiral deposits. Thus, for instance, 

 in all my inquiries into the structure of the ligneous body, 1 

 have never contented myself with comparing the parts of 

 different age of the same individual, but have constantly, 

 as far as the material was at my disposal, at the same time 

 pursued throughout a whole year the development of the 

 same annular ring, by regularly repeated observations on the 

 most varied parts of the plant. Highly instructive likewise 

 is an accurate history of the development of the Spiroidea 

 in the large Monocotyledonous vascular bundles, for instance, 

 in Arundo Donaoc, where it must also be borne in mind not 

 merely to compare on the same individual the younger with 

 the older internodes, but to examine the homologous inter- 

 nodes on several individuals of different age. In this plant 

 the spiroidea are situated in the perfectly developed fasciculus 

 in a series radial from the axis to the periphery, arranged 

 between the two large so-called porous vessels. The an- 

 nular vessels, w r ith the rings furthest from one another, are 

 nearest to the axis of the internode, from thence towards the 

 circumference the rings approach closer together, then pass 



