4 oo SCIENCE PROGRESS. 



Stem of Catamites" show a ring of small groups of xylene 

 elements, and in connection with each strand of tracheae 

 a comparatively large canal. The resemblance of such stems 

 to that of a recent Equisetum is exceedingly close, and it is 

 rendered still more real by the occurrence in the carinal 

 canals of fragments of annular, spiral, or more rarely 

 reticulate tracheids. Solms-Laubach, 1 in describing the 

 structure of Catamites, suggests that " in the lacunae, or the 

 tissue that fills them, we are dealing with the tracheal 

 initial strand of the primary bundle " ; the observations of 

 Cormack, Scott, Williamson, and Hick have fully con- 

 firmed this rational interpretation of these Equisetum-like 

 canals. The nature of the primary xylem structure is 

 admirably shown in an oblique transverse section figured 

 by Williamson and Scott. 2 The phloem of the primary 

 bundle has not been made out in any detail ; in describing 

 an exceptionally good section of a young stem, Hick refers 

 to certain small elements external to each canal, "which, 

 from their position and their distinct character, . . . must 

 be regarded as the phloem of the primary bundles " ; 3 in a 

 longitudinal section these elements are found to have a 

 narrow elongated form. There is no direct evidence of 

 any particular tissue which can be designated a pericycle, 

 nor is it possible to demonstrate satisfactorily the existence 

 of an endodermal layer. Williamson and Scott refer to 

 several specimens in which the innermost cortical layer 

 consists of regular thin-walled cells, fairly distinct from the 

 rest of the tissue, and Hick figures and describes a sharply 

 defined black line passing round the stem in a position 

 suggestive of an endodermis. 



The greater part of the cortex of a young branch 

 consists internally of parenchyma, with occasional cells full 

 of carbonaceous matter, and which are probably secretory 

 sacs. Occasionally the more external parts of the cortex 

 are made up of small parenchymatous cells with scattered 

 thick-walled elements, and the outermost layer or epidermis 



1 Fossil Botany, p. 298. Oxford, 1891. 

 2 PL Ixxvii., fig. 4. 3 Hick (2), p. 161. 



