Structure of the Leaves of Calamites. 189 



with the primary structure of the stem * I suggested that 

 this was an important tissue, and this is confirmed by its 

 presence in the leaves. As to its physiological import, 

 there is little to add to what was then stated. The view 

 that it had a conducting function receives additional sup- 

 port from the details given of its position and characters 

 within the leaf, and from the fact that it is continuous from 

 the one to the other. Moreover, it is highly significant, in 

 my opinion, that in the stem it lies at the inner boundary 

 of the Cortex, and appears to correspond in position with 

 the " starch layer" of many recent plants. In the leaf, too, it 

 seems to form a sort of sheath round the stele, and is in 

 intimate relation on the one hand with the delicate vascular 

 bundle, and on the other with the assimilating tissue. 



Finally a word may be said as to the type of Calamites 

 to which these leaves are to be referred, since it is becoming 

 more and more evident that the plants now included in the 

 genus are not identical in the minuter details of their 

 structure. The type of stem dealt with in my former 

 paperf is the one which appears to predominate in the 

 Lower Coal Measures of Halifax, whence most of the 

 specimens have been obtained, and it is to this that the 

 leaves here described are to be referred. The presence of 

 the peculiar " melasmatic " layer in both stem and leaf 

 would of itself be almost sufficient to justify this reference, 

 but it is placed beyond doubt by the fact that the twigs 

 found in connection with some of the leaves are of the type 

 in question. As in the paper mentioned, reasons were 

 adduced for regarding this type of Calamites as the one 

 which had Calamostachys Binneyana for its fruit, we may 

 with some confidence look upon this type as one whose 

 organisation is now fairly well known, except so far as 

 there may be special peculiarities in the root. 



* Memoirs and Proceedings of the Manchester Lit. and Fhii. Soc. 4th 

 Series, Vol. VIII., pp. 158-170. 



+ Loc. cit. 



