1871.] 



DAWSON — DEVONIAN TRBE FERNS. 



275 



Fig. 6. Protopferis peregrina, Newberry, imprpHsion of stem, one-fourth the 

 natural size : xx, remains of petioles. [> a, soar, natural size, show- 

 ing bundles of vesHels at base ; 5 />, portion of a vascular bundle, mag- 

 nified, showing scalariform vessels and cellular tissue; 6c, scalari- 

 form vessel, highly magnified. 



Fig 6. Lower part of stem of the same, with aerial roots, one fourth the na- 

 tural size. a, one of the roots, natural size. 



Fig. 7. Vascular bundle of liachiopteris, natural size ; 7 fl, portion of the same, 

 showing vascular and cellular tissue, witli rounded granules in the 

 cells ; 7 f>, one of the cells magnified, showing containMl granules. 



Fig. b. Naggerathia gilboensia, one-hali the natural size. 



DiSCTTSSION. 



Dr. Duncan doubted the desirability of basing generic and specific 

 terms on imperfectly preserved and indistinct specimens, and pointed 

 out the disagreements among botanists that had resulted from so 

 doing. He would prefer calling fossils such as those described 

 " cryptogamous forms from certain strata." He was doubtful also 

 whether the supposed petrified starch was not merely orbicular 

 silex. 



The Chairman (Prof. Morris) remarked on the four different con- 

 ditions exhibited by existing tree ferns : — first, with roots running 

 down the stem ; secondly, the lower portion with oval scars ; these 

 are, thirdly, further up the stem, rhomboidal vertically ; and, fourthly, 

 higher up still, rhomboidal horizontally ; so that were the plant fossil, 

 distinct genera and species might be founded upon the different parts. 



