XXX] SUTCLIFFIA 153 



internal to the hypoderm is a row of leaf-bundles (fig. 439, A) 

 each of which is accompanied by stereome strands. 



The petioles, which reach a diameter of 12 cm., contain 

 numerous, occasionally anastomosing, concentric bundles. Nothing 

 is known of the fronds as a whole beyond the fact that they are 

 spirally disposed and had decurrent bases of large dimensions in 

 proportion to the stem. 



Sutcliffia insignis, forma J3. 



This form, described by Miss de Fraine as Sutcliffia insignis 1 , 

 is represented by a stem rather smaller than the type-specimen 

 described by Scott, though it is probably an older example of the 

 same species. It is distinguished by a greater development of 

 secondary xylem and phloem both on the main stele and the 

 meristeles; it differs also in the absence of the greater part of 

 the cortex and leaf-bases which have been cut off as the result 

 of the formation of a deep-seated periderm (fig. 439, D, C). The 

 meristeles are smaller and fewer than in the larger form and are 

 distinguished by some other peculiarities. At m' in fig. 439, D, 

 a meristele is seen attached to the main stele. In Sutcliffia 

 insignis forma a the main stele is enclosed by an irregular network 

 of subsidiary steles or meristeles and these form the points of 

 departure of the leaf-traces, but the meristeles are not completely 

 used up in the process of conversion into leaf-traces. In Sutcliffia 

 insignis forma f$ the meristeles agree in structure with the main 

 stele except in the smaller amount of secondary tissue : they 

 do not, however, form a network as in. forma a but occur as strands 

 parallel to the central stele, 'giving off leaf- traces and ultimately 

 dividing up into smaller strands, often unequal in size, the primary 

 wood of the meristeles being entirely used up in the production 

 of radially symmetrical or unilateral bundles.' In this respect, 

 as Miss de Fraine points out, forma fi agrees more closely than 

 forma a with Medullosa anglica and supports Scott's view that 

 Sutcliffia is a primitive type of Medullosan stem. The leaves were 

 given off at fairly long intervals as in some species of Medullosa : 

 the leaf-traces are exarch and similar to those of the type-species. 

 The most striking feature of the new stem is the presence of a 



1 de Fraine (12). 



