420 BENNETTITALES [CH. XXXVI 



lost the finer pitting of the sieve-plates. The fibres are more or 

 less square in transverse section and have excessively thick walls, 

 the lumen being reduced to a small hole. Parenchymatous cells 

 (fig. 540, a) occupy the angles between the sieve-tubes and 

 occasionally stretch tangentially between a pair of tubes : these 

 are compared by Dr Stopes to companion-cells, but their manner 

 of occurrence hardly justifies the interesting suggestion that they 

 may be precursors of the Angiosperm companion-cells. The 

 medullary rays may be as wide as the elements which they traverse ; 

 they are characterised by their wavy walls, as seen in radial 

 longitudinal sections; no pitting was noticed. A remarkable 

 feature of the specimen is its considerable breadth : it is pointed 

 out that in a giant stem of Sequoia with a girth of over 40 ft 

 the secondary phloem does not exceed 3 4 mm. in breadth. 

 The great thickness of the phloem in the fossil suggests comparison 

 with the corresponding tissue in recent and fossil Cycadean stems, 

 and the alternation of hard and soft phloem is a feature exhibited 

 also by Cycadeoidea Gibsoniana (fig. 518, B). Dr Stopes con- 

 cludes that the phloem is in the main similar to that in some 

 Cupressineae, Taxineae, and Taxodineae. It is noteworthy that 

 similar phloem with sieve-tubes and fibres associated with cork 

 is described by Graf Solms-Laubach 1 from Upper Jurassic beds 

 in Franz Josef Land. The systematic position of Vectia cannot 

 be definitely determined, but I believe that it is more closely 

 allied to Cycadean than to Coniferous phloem. 



NOTE. It is unfortunate that Mr Wieland's second volume 

 dealing with American Cycads [Wieland (16)] did not come into 

 my hands until nearly the whole of this volume was in type. 

 Students will find in it many additions to our knowledge of 

 Cycadeoidea and Williamsonia, much theoretical discussion that is 

 suggestive and interesting, useful summaries of our knowledge of 

 fossil Cycads, and many beautiful photographic plates illustrating 

 the morphology of American species of Cycadeoidea. 



1 Solms-Laubach (04) p. 12, PL n. figs. 5, 6. 



