396 Professor Buckland on the Ci/cadeoidas, a Fumili/ of Fossil Plants 



the structure of coniferous wood*. The limestone adjacent to these trees is 

 itself pervaded by silex,, and contains beds and nodules of chert. 



On my submitting our new fossils to Mr. Brown and Mr. Loddiges^ they 

 immediately recognised a resemblance to the genera Zamia and Cycas, which 

 compose the existing family of Cycadeae, a resemblance which further investi- 

 gation has tended fully to establish : and as their structure will be best explained 

 by comparison with fhe recent Zamia and recent Cycas^ I have given transverse 

 sections of them both, wherein we find remarkable analogies to the two fossil 

 species we are about to establish f. In the Zamia horrida of the Cape of Good 

 Hope the transverse section exhibits one narrow circle, composed of radiating 

 plates, placed in the cellular substance that forms the stem or body of the plant; 

 and nearly at equal distance between its centre and circumference J, and in a 

 section near the base of Cycas revoluta§, we have two narrow circles of radia- 

 ting plates, placed also in the cellular substance that forms the stem, and both 

 of them nearer to the centre than to the circumference of the plant ; the 

 outermost of these circles is the most narrow. 



Neither Zamia nor Cycas has any covering of true bark, but the stem is 

 inclosed in a thick case made up of the persistent bases of decayed leaves : 

 each of these terminates externally in a lozenge-shaped impression or scar, the 

 convex surface of which formed the joint from which a leaf had fallen off. A 

 dense and continuous series of these leaf-joints entirely surrounding the stem 

 gives it more the appearance of a pine-apple or enormous fir-cone, than of a 

 vegetable trunk ||. On comparing these peculiarities of structure with those 

 displayed in our fossil specimens, we recognise a correspondence highly cu- 

 rious and satisfactory. Like the recent Cycadeas, our fossil stems are inclosed 

 in no true bark, but have a thick case made up of the flat persistent bases of 

 decayed leaves, which at their inner extremity touch the cellular tissue of the 

 body of the trunk, and terminate externally in an oblong gibbous joint resem- 

 bling the leaf-joints of Zamia horrida^. These bases of leaves rise upwards, 



* Dr. Fitton has recently discovered a fossil much resembling a small strobilus, about two 

 inches long and one inch and a half wide, in the quarries of Quainton near Aylesbury, which are 

 probably in the same formation as those of Portland. 



f There are five known species of Cycas, and about seventeen species of Zamia, which Persoon 

 has grouped together into the family of Cycadca;. The difficulty that has attended the arrange, 

 ment of this family from its intermediate place between the ferns, the palms, and the Coniferae, to 

 each of which it possesses certain points of approximation, and the discussions respecting it which 

 still occupy some of the most eminent botanists of our day, give a peculiar interest to the discovery of 

 fossil plants so nearly allied to the Cycadeae as those which form the subject of the present memoir. 



i Plate XLVI. fig. 3. § Ibid. fig. 1. )| See Plate XLVI. fig. 4. 



1 See Plate XLVII. fig. 4. 



