Manchester Memoirs, Vol. Ivii. (1913), 7V^. 18. 3 



The size and general external appearance of the fossil 

 exhibited by Mr. Coward is in close agreement with one 

 of the periodic enlargements of Tylodendron. There are, 

 however, certain internal features in which this plant 

 differs from those described by Potonie and which warrant 

 a careful description of its structure. 



A transverse section through our specimen shows that 

 except for a few longitudinal fissures the tissues are 

 fairly well preserved throughout the specimen, though the 

 tissues do not allow of the most detailed examination. 

 Almost the entire mass consists of pith or medulla, but 

 along the circumference there are disconnected masses of 

 lignificd tissue consisting of the wood}^ tissues of the stem. 



The pith is seen to be composed entirely of thin- 

 wallcd parenchyma similar to that described by Potonie. 

 The cells are polygonal, more or less isodiametrical in 

 shape, sometimes, however, slightly longer in a horizontal 

 direction, while towards the outside, where they approach 

 the protoxylem, the long axis of the cells is parallel to 

 that of the woody elements. The size of the parenchyma 

 cells varies from 8-1 i/u in their shorter diameter and 

 from 15 to i6|U in their longer diameter. The outer 

 portions of the pith have very numerous secretory canals 

 with dark brown contents, very like those found in the 

 Medullosae, in C}'cads, and also in the pith of Poro- 

 xylon. These have not been observed or described, as 

 far as I know, in any other specimens of Tylodendron 

 showing structure. Each of these ducts is surrounded by 

 eight or more cells, often slightly radiate in their arrange- 

 ment, of large parenchymatous type, similar to those of 

 the rest of the pith (see PL II., Ftg. i). The canals are 

 always filled to some extent by a darker coloured mass, 

 probably the remains of whatever secretion they contained. 

 In longitudinal section they are seen as long and con- 



