ROOTS OF CALAMARIEAE 41 



branches ; the larger leaves, however, are practically 

 unknown in the petrified condition. In Fig. 14 a 

 tranverse section of a bud, showing a number of the 

 leaves arranged in whorls around the axis, is represented, 

 They have the same form in transverse section as Pinus 

 leaves. In the middle there is a collateral vascular 

 bundle, usually with the wood alone preserved. The 

 bundle is surrounded by a pericycle of thin-walled 

 parenchyma, and outside this we find a sheath of large 

 cells containing carbonaceous matter, perhaps derived 

 from some product of secretion. Long cells, radiating 

 out from the central cylinder, form a definite palisade- 

 tissue, presumably the assimilating layer ; at the 

 periphery is an epidermis, in which the stomata are 

 sometimes clearly shown. This is a perfectly simple 

 and straightforward type of leaf, and it is sometimes 

 very well preserved. There is thus no difficulty as 

 regards the structure, in the case of the leaves, of very 

 small size, which were borne on the slender twigs of 

 Calamites. There is a great resemblance between the 

 vegetative leaves and the bracts of Calamarian cones. 



6. The Roots. — As regards the roots of Calamarieae, 

 we are now in possession of a considerable stock of 

 information. In Williamson's paper of 1871 — the first 

 of his Royal Society series — among the varieties of 

 Calamites the author described some specimens which 

 differed from the ordinary form, for they had a solid 

 pith and no fascicular canals. In a later memoir he 

 distinguished organs of this type under the generic 

 name of Astromyelon. In the meantime Messrs. Cash 

 and Hick had found some beautiful specimens with the 



