144 Palaeontologie. 



from one corner of the wood; he interpreted this Strand as the 

 bündle running to a lateral rootlet. The rootlets of Stigmaria. 

 however, are known to branch by dlchotomy, and Renault 's 

 Observation has not hitherto received any confirmation. Prof. 

 Weiss, in the present paper, demonstrates that the vaseular 

 Strands seen by Renault occur frequently in Stigmaria n 

 rootlets, though he finds that they have no relation to 

 branching. The vaseular Strand starts from the protoxylem of 

 the rootlet-stele, and passes outwards, transversely or obliquely, 

 enclosed in a parenehymatous sheath, until it reaches the inner 

 layers of the external cortex. Here it terminates in a group 

 of wide and short tracheides with delicate spiral or reticulate 

 markings. 



There is evidence that the Strand sometimes branched and 

 may thus have been connected with more than one of these 

 cortical patches of tracheides. The whole arrangement, of 

 which the author describes several modifications, is compared 

 by him with the transfusion-tissue which is known to be 

 present in the Ieaves of Lepidodendreae. But in the case of 

 the rootlet, as he points out, the funetion was doubtiess that of 

 the absorption of water, while in the leaf it served for the 

 transmission of water outwards. The only recent roots which 

 offer any counterpart to this strueture, are the highly modified 

 roots of certain parasitic Phanerogams, described by Solms- 

 Laubach. 



That the rootlets of Stigmaria shouid have required some 

 special adaptation for the absorption of water appears probable 

 from a consideration of their strueture. In some cases the thin 

 radial band of parenehyma through which the vaseular Strand 

 passed was the only connection between stele and outer cortex ; 

 in other cases the vaseular Strands themselves may have 

 constituted the sole means of communication. 



In conclusion, the author suggests that the existence of 

 tracheids comparable with transfusion cells in the appendages 

 of Stigmaria may be regarded by some botanists as an 

 additional argument in favour of the foliar homologies of these 

 organs. He does not himself aeeept this view, but regards the 

 appendages as true rootlets, provided with a highly specialized 

 apparatus for the absorption of water. d. H. Scott (Kew). 



Ausgegeben: lO. Februar IS03. 



Commissions -Verlag: E. J. Brill in Leiden (Holland). 

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