244 CONIFEEALES [CH. XLIV 



XV. PLANOXYLON. Stopes. 



Dr Marie Stopes ^ has recently instituted this generic name for 

 a piece of Coniferous wood from Middle (or Upper?) Cretaceous 

 rocks in New Zealand and in it she also includes the Liassic species 

 Araucarioxylon Lindleii (Witham). The genus is a striking ex- 

 ample of a combination of Araucarian and Abietineous characters^, 

 and, as Dr Stopes points out, it resembles in this respect Cedroxylon 

 transiens Goth, and other generalised types. 



Planoxylon Hectori Stopes. The type-specimen, from Amuri 

 BlufE, New Zealand, is part of a stem 150 years old or more. The 

 lings of growth are well marked ; the tracheids have 1 — 3 rows of 

 alternate and hexagonal bordered pits on the radial walls and there 

 may be a single row of separate pits on the elements at the end of 

 an annual ring. The medullary rays are nearly always uniseriate, 

 1 — 24 cells deep but usually from 3 to 9 cells in depth ; all the 

 walls of the ray cells are pitted and there are 1 — 2 vertical rows of 

 three pits in the field in the neighbourhood of the spring tracheids 

 and generally a single vertical pair in the region of the late wood. 

 Xylem-parenchyma appears to occur only between the spring 

 tracheids and the latest formed wood of the previous year. Like 

 many other fossil stems this species indicates the existence of 

 Conifers with typical Araucarian pitting on the tracheids and 

 equally well defined Abietineous pitting on the medullary-ray cells. 

 It is especially interesting as showing the presence in the southern 

 hemisphere of a type very similar to Cedroxylon transiens and other 

 species recorded from high northern latitudes. 



Planoxylon Lindleii (Witham). 



This Liassic species from Whitby was originally referred by 

 Witham' to the genus Pence ; subsequently included in Araucario- 

 xylon* it has recently been transferred by Dr Stopes to her new 

 genus Planoxylon^. The pitting of the tracheids is essentially 

 Araucarian; there are 1 — 3 rows of alternate hexagonal pits on 

 the radial walls, but the pitting of the medullary-ray cells, as 

 Dr Stopes has shown, is typically Abietineous. 



1 Stopes (16) 



= Ti-Xavaofiai, to wander; suggesting that 'the forms comprising the genus were 

 moving from one position to another in a systematic sense.' 



3 Witham (33) A. p. 58, Pis. ix., xv. « Seward (04) B, p. 56, Pis. vi., vn. 



^ Stopes (16) pp. 118, 120, text-figs. 6, 7. 



