XIIl] TMESIPTERIS 23 



distinctly favour the view that a sporophyll is best interpreted 

 as a stalked leaf with two sterile laminae and an almost sessile, 

 or in some cases a more obviously stalked, synangium; the 

 whole sporophyll is characterised by the possession of a ventral 

 and a dorsal lobe*. The drawings reproduced in fig. 120, D 

 and F, illustrate some of the frequent variations described by 

 Thomas in plants which he observed in the New Zealand 

 forests. The sporophyll shown in fig. 120, D and F, has 

 branched twice and bears three synangia. 



The aerial branches of Tmesipteris possess a central 

 cylinder of separate xylem groups in which the protoxylem 

 occupies an internal position (fig. 120, C and E, px) enclosing 

 an axial parenchymatous region. The cells of a few layers of the 

 inner cortex immediately outside the endodermis are rendered 

 conspicuous by a dark brown deposit. The cortex as a whole 

 is composed of uniform parenchymatous tissue. In the lower 

 part of the aerial shoots and in the rhizome the xylem forms 

 a solid strand without protoxylem elements and conforms more 

 clearly to that of Fsilotum. 



In this short account of the anatomy of Tmesipteris no 

 mention is made of the effect produced on the stele by the 

 departure of leaf-traces and of vascular stands to supply 

 branches. Miss Sykes^ in a recently published paper on the 

 genus has shown that the exit of a leaf- trace does not break 

 the continuity of the xylem of the stele, while the exit of a 

 sporophyll-trace is marked by an obvious gap. Evidence 

 is adduced in support of the conclusion that this difference, 

 which at first sight appears to be one of morphological import- 

 ance, is in reality merely a question of degree and " is due to 

 the earlier preparation for the formation of 'sporophyll' than 

 leaf-traces." Miss Sykes gives her adherence to the view that 

 the "sporophylls" of Tmesipteris are branches and not leaves, but 

 despite the arguments advanced this interpretation seems to 

 me less probable than that which recognises the sporophyll as 

 a foliar organ. Prof Lignier^ has pointed out that if Miss 

 Sykes's conclusion as to the axial nature of the sporophyll in 

 Tmesipteris is accepted, it diminishes the force of the com- 

 1 Sykes (08). ^ ^5^^. (08). ^ Lignier (08). 



