196 CAIiAMOPITyBAB [CH. 



Through the kindness of Prof. Bower I have had an opportunity 

 of examining sections from the older horizon in his possession. 

 The transverse section reproduced in fig. 456 has a diameter of 

 3-8 X 2-2 cm.i : on one side the radially placed plates of stereome 

 are clearly shown, and in the outer portion of the ground-tissue 

 is a ring of vascular bundles varying in size and shape but with 

 a general tendency to a radially elongated form. The ground- 

 tissue consists of homogeneous parenchyma: in one place I 

 noticed what appeared to be a large secretory canal, but secretory 

 tissue, generally at least, is unrepresented. The xylem is com- 

 posed of imperfectly preserved elements, which appear to have 

 scalariform pits; spiral protoxylem strands, embedded in the 

 metaxylem as two or four groups, occur near the ends of the 

 long axis of the bundle and in some cases also near the centre. 

 The phloem probably surrounded the xylem, though it is not 

 certain whether the arrangement was collateral or concentric: 

 there are no secondary-xylem tracheids, though in some places 

 I noticed a tendency to a radial disposition of cells at the periphery 

 of the vascular tissue simulating an early stage of secondary growth. 

 Unger's second species Kalymma striata is characterised by an 

 arrangement of the bundles similar to that in a petiole described 

 by Scott and Jeffrey as Calamopteris Hiffocrefis which difiers 

 from Kalymma in the partial substitution of bands of vascular 

 tissue for separate bundles and to some extent in the disposition 

 of the bundles. The two types of petiole Kalymma and Cala- 

 mopteris, as Scott and Jeffrey state, are very closely allied. Dawson 

 and Penhallow^ have also described Kalymma grandis from 

 Kentucky but they, Kke Unger, mistook the hypodermal stereome 

 for an outer zone of vascular bundles. The petioles from Germany 

 and North America included under the name Kalymma grandis, 

 though too similar to be referred to different species, no doubt 

 represent petioles of stems which are unquestionably distinct 

 types: as in the case of Myeloxylon in its relation to the genus 

 Medullosa, Kalymma stands for several closely allied forms of 

 petioles belonging to several species of Calamopitys. 



1 Scott and Jeffrey (14) p. 328, refer to a speoimeu over 6cm. in diameter; 

 these authors give several excellent figures of Kalymma. 



2 Dawson and Penhallow (91). 



