BY THE REV. J. E. TENISON-WOODS, F.G.S., F.L.S. 67 



pretty and ornamental appearance. The following is the explana- 

 tion of their structure : In the stems of Equesetacese there is a 

 double series of lacuna or longitudinal empty spaces, the exterior 

 of which corresponds to the external ribs, and the interior to the 

 grooves. In Lindley and Hutton's Fossil Flora, vol. 3, p. 186 

 (plate 180), there is a figure of one of these diaphragmata 

 magnified. It w r as described by them as Equisetum laterale, 

 though with the observation that the authors were by no means 

 sure that it was an Equisetum. " What is most remarkable," say 

 the authors " at irregular distances between the articulations are 

 found little round disks with lines radiating from a common centre, 

 something in the way of the phragma of a Ccdamites. These disks 

 which look like the scars left behind the branches that had fallen 

 off, are not stationed at the axils or articulations, but appear at 

 uncertain intervals along the internodes, and are found less 

 frequently on the stem than loose in the shale, without any 

 apparent connection with the plant. This is a singular fact, and 

 would lead one to think that the disks hardly belong to the stems 

 with which they are found associated. 



With regard to the same I translate the following from Schimper 

 (vol. 1, p. 285). "The radiating disks that are seen in so many 

 specimens above the articulations, and which have given the species 

 its name, have been figured and described by authors without 

 explanation, or as the scars of the branches. But they are only 

 the impressions of the diaphragmata, either reversed or somewhat 

 pressed out above. The same thing is constantly seen in Annularia 

 and even in Equisetum, amongst others in Equisetum miinsteri, 

 where the large circular impressions have been equally taken for 

 branch scars. The description given by the authors of the fossil 

 flora agrees well with the character of diaphragmata, and not with 

 those of scars. M. Andre * figures a diaphragm surmounting 

 a reversed diaphragm. Many of these disks are scattered over 

 the same piece of stone. M. Andre considers these as isolated 



* Foss. Flora Siebenburgens u. des Banates, plate VI. Equisetites 

 lateralis. 



