1 88 Mr. Thomas Hick on the 



that they were young and immature, but the histological 

 structure shows few or no indications of the embryonic 

 condition. Figures 5 and 6 are, perhaps, a little doubtful 

 on this point, and it may be that the leaves of Fig. 2 have 

 not reached their full development. But there is nothing 

 to indicate immaturity in the structure of the leaves shown 

 in Figs. 3, 4, and 7, and the same may be said of a large 

 number of similar sections that have been passed in review. 

 In the literature, it is generally stated that the members 

 of each whorl of leaves are quite free, and destitute of any 

 cohesion at the base comparable to that seen in Equisetum. 

 My observations on the structure of the leaves is in full 

 accord with this statement, and show that they were simple 

 uni-nerved structures. The vascular bundle, however, is so 

 delicate, and occupies such a position within the mesophyll, 

 that it could scarcely give rise to the appearance of a 

 midrib in cases where fossilisation resulted in the formation 

 of a mere impression. Such an appearance, however, might 

 be produced by the strand of sclerenchyma, which has been 

 described as running for some distance along the middle 

 line cf the leaf, between the vascular bundle and the upper 

 epidermis, as shown in Fig. 7, or by the median ridges 

 shown in Figs. 5 and 6. 



The extremely small size of the leaves and the twigs 

 that bore them enable us to form some idea of the delicate 

 and filmy appearance that would be presented by the 

 ultimate ramifications of the type of Catamites to which 

 they belonged. This is, in a measure, represented in some 

 of the restorations of Catamites that have come under my 

 notice, but none seem to me to have done it full justice. 

 The most likely comparison that occurs to me is that of 

 well-grown Chara plants as seen in our laboratory aquaria. 



As regards the structure of the leaves, the details given 

 will show that it has many points of interest, not the least 

 being the presence of the "melasmatic" tissue. In dealing 



