328 



PROE. A. C. SEWARD AND MR. J. WALTON ON [vol. lxXlX, 



sheath of specialized tissue internal to the primary bundles of 

 wood which project into the medullary region. Growth-rings 

 very distinct. Medullary rays typically uniseriate, 1 to 16 cells 

 in depth. Tracheids with uniseriate to triseriate bordered pits 

 on the radial walls, sometimes in stellate groups, generally in 

 contact, but frequently distant ; when more than one row of pits 

 occur, the pits of adjacent rows may be alternate or opposite. 

 Pits in the field simple, varying from one large, slightly elliptical 

 pit to several smaller pits ; the long axis of the ellipse is horizontal 

 in the latter, which are pits on the wall of the ray-cell. 



Locality. — Falkland Islands, Choiseul Sound. Associated 

 with Glossopteris. 



lame. 



Horizon. 



Rings. 



Pits 

 fraeheidi in the 

 pits. J Field. 1 



1 

 Pith. 



Callixylon 3 spp. (North 

 America.) 



Devonian. 



Slight. 



1-4 rows. 



Small, 

 numerous. 





Dadoxylon indicum Hol- 

 der!. (India.) 



Permo-Carb. 

 (Damuda.) 



Well- 

 marked. 



1-2 



Large, few. 



Secretory 

 cells. 



Dadoxylon Sakeri,f>Y>. now 

 (Falkland Is.) 



Permo-Carb. 



Well- 

 marked. 



1-4 



Large, few. 



Secretory 

 cells. 



Dadoxylon Tchihatcheffi 

 Gceppert. (Europe.) 



Permo-Carb. Well- 

 marked. 



1-3 





Secretory 

 cells. 



Dadoxylon lafo}iiense 

 Halle. (Falkland Is.) 



Permo-Carb. . Well- 

 marked ? 



1-2 





Secretory 

 cells. 



Dadoxylon nummul arium" 

 White. (South America.) 



Permo-Carb. Indistinct. 



1 



1, distant. 







Dadoxylon meridionals 3 

 White. (South America.) 



Permo-Carb. 



Absent. 



1, distant. 







Dadoxylon Arberi (=D. 

 australe Arher). 4 (Aus- 

 tralia.) 



(Paleozoic.) 



Well- 

 marked. 



1, multi- 

 seriate. 



Numerous. 





Dadoxylon sp. 5 (South 

 Africa.) 



Ecca. 



Well- 

 marked. 



1-2 



Large, few. 





Dadoxylon sp. 6 Warren. 

 (South Africa.) 



? Upper Ecca J 



1-3, often Small, 

 distant. 





Rhexoxylon sp. (Africa.) 



Stormborg. IWell- 



\ marked. 



1-2 Large, few. 'Secretory 

 I cells. 



1 



Conclusion. 



I. Devonian plants. — The fragmentary remains described 

 by Dr. Halle and the specimens collected b} r Dr. Baker from 

 Halfway Cove and Port Purvis respectively, though not sufficiently 



1 Authors do not usually state whether the pits are on the tracheid or on 

 the medullary ray -cell. 



2 White, D. (08) pi. xiii. 



3 White, D. (08) pi. xiv. 



4 Arber (05) p. 191. Reasons for substituting the specific name Arberi 

 for australe are given in A. C. Seward's ' Fossil Plants ' vol. iv (1919) p. 178. 



5 Arber (10). 



6 Warren (12) text-fig. 1 B, p. 353. 



