344 Mr Seward, On Encephalartos Ghellinckii, etc. [Nov. 8, 



resemblance, in the scattered collateral bundles and large canals, 

 to the fossil petioles known as Myeloxylon. The hypoderm in the 

 younger portion of a rachis consists in part of collenchyma, which 

 afterwards developes into uniformly thickened fibrous tissue. 



The following points may be briefly noticed in the anatomy of 

 the pinnae. In tranverse section a pinna has the form of a 

 somewhat flattened crescent, the two edges being bent over 

 towards the under surface. The upper surface is covered by a 

 thick cuticle, and the epidermis is succeeded by two or three 

 layers of thick-walled fibres, and internal to these there is exceed- 

 ingly well-marked palisade tissue of one layer of long cells ; 

 internal to this the mesophyll consists of spongy parenchyma 

 followed by one or two rows of fibres and the lower epidermis. 

 There are numerous stomata on the lower surface, the two guard- 

 cells being situated at the bottom of a fairly deep depression. The 

 mesophyll is traversed by four collateral bundles surrounded by a 

 ring of fibrous elements. The woolly appearance of the young 

 fronds is due to the occurrence of numerous long unicellular hairs 

 borne on a short and thick-walled stalk-cell as in Divon edule, 

 Lind., and other Cycads 1 . 



The importance of such a species as Encephalartos Ghellinckii 

 in connection with fossil Cycads has previously been discussed. 

 The necessity of examining as many recent species as possible, 

 especially the less known and rarer forms, cannot be too strongly 

 urged. There are several fossil fronds in which the rachis bears 

 numerous long and narrow pinnae, which may well be compared 

 with Encephalartos Ghellinckii. Some of the Mesozoic fronds, 

 which have been erroneously referred to the genus Cycadites 2 , 

 bear a very close resemblance to those African Cycads with the 

 narrow linear or linear-filiform segments. 



1 My thanks are due to Mr A. W. Hill, of King's College, for preparing several 

 sections of the frond of Encephalartos Ghellinckii and other species. 



2 For references to fossil fronds vide Wealden Flora, vol. n. pp. 36 et seq. 



