CYCADEAE, MEDULLOSEAE. 95 



form a broad horse-shoe arrangement open above and with very short 

 shanks inclined inwards. In some cases the parenchyma has partially 

 disappeared (rotted out) on the surface of separation, and then the leaf- 

 bases appear from the outside as rhombic cavities surrounded by a pro- 

 jecting network, which is formed by the silicified epidermal layers and 

 the masses of paleaceous hairs lying between them. Similar conditions 

 of preservation occur also in other stems of Cycadeae, as, for example, 

 in Clathropodium foratum l , which may perhaps belong to Bennettites and 

 which derives its name from them, and in Raumeriae also which will be 

 noticed again further on. 



But in Bennettites this armour of leaf-bases is pierced by many 

 tightly-closed flowers or inflorescences, which surrounded by numerous leaves 

 force their way through it and come to the surface, and there owing to the 

 rubbing off of the tips of their leaves between the surfaces of separation of the 

 leaf-bases appear in the form of peculiar centrically constructed whorls. It 

 is at present uncertain whether these organs arise as axillary buds, though 

 this is in itself probable ; some other points also connected with their 

 structure are still undetermined, notwithstanding Carruthers' excellent 

 and searching examination of this fossil. The courtesy of Messrs. Car- 

 ruthers, Hooker and Thiselton Dyer has put me in a position to make 

 a fresh examination, and this has already cleared up some of these questions 

 in a satisfactory manner. I must however reserve descriptive details for 

 the connected account of the stem, which I design to give. The entire 

 object is attached to the rind of the stem by a thick stalk, which is sur- 

 rounded by lanceolate leaves 2 and repeats even the details of the structure 

 of the stem on the small scale, showing only some irregularity of shape in the 

 transverse section in many places, due probably to pressure. The leaves also 

 which encircle it are distinguished from the before-mentioned leaf-bases of 

 the main axis only by the smaller and constantly decreasing size of the trans- 

 verse section. The stalk terminates in a flatly convex cushion, which I 

 conclude to have been of a fleshy succulent character 3 , because its tissue 

 has been wholly destroyed, and consequently nothing can be perceived 

 in the preparation before me but confused macerated parenchyma-cells and 

 fragments of vascluar bundles. From the upper surface of the cushion 

 there arises a bundle of closely crowded polygonal stalks in an envelope 

 of several layers of linear-lanceolate leaves ; the stout cortical parenchyma 

 of these stalks has protected them from decay, and forms a sheath round 

 the small vascular bundle which lies in the middle of a gap in the tissue. 

 Between these stalks and filling small interstices are seen other transverse 

 sections, each of which conceals a vascular bundle (Fig. 5 C). Whether 



de Saporta (4), vol. ii. " Carruthers (4), t. 58, ff. 5 and 3. 3 Carruthers (4), t. 59, f. 3. 



