FOSSIL CYCADE^ IN DORSETSHIRE. 371 



the recognition of similar structures in fossil plants, refera- 

 ble to a family whose characters are so remarkable. 



The figure of a Cycas revoluta (PL 58,*) represents the 

 form and habit of plants belonging to this beautiful genus. 

 In the magnificent crown of graceful foliage surrounding 

 the summit of a simple cylindrical trunk, it resembles a 

 Palm. The trunk in the genus Cycas, is usually long. That 

 of C. circinalis rises to 30 feet.f In the genus Zamia it is 

 commonly short. 



Our figure of a Zamia pungens,J (PI. 59,) shows the mode 

 of inflorescence in this Genus, by a single cone, rising like 

 a Pine Apple, deprived of its foliaceous top, from within the 

 crown of leaves at the summit of the stem. 



The trunk of the Cycadeje has no true bark, but is sur- 

 rounded by a dense case, composed of persistent scales 

 which have formed the basis of fallen leaves ; these, to- 

 gether with other abortive scales, constitute a compact 

 covering that supplies the place of bark. (See PI. 58 and 59.) 

 In the Geol. Trans, of London (vol. iv. part 1. New 

 Series) I have published, in conjunction with Mr. De la 

 Beche, an account of the circumstances under which silici- 

 fied fossil trunks of Cycadeai are found in the Isle of Port- 

 land, immediately above the surface of the Portland stone, 

 and below the Purbeck stone. They are lodged in the 

 same beds of black mould in which they grew, and are 

 accompanied by prostrate trunks of large coniferous trees, 

 converted to flint, and by stumps of these trees standing 

 erect with their roots still fixed in their native soil. (See 

 PI. 57, Fig. l.§) 



* Drawn from a Plant in Lord Grenville's Conservatory at Dropinore, in 

 1832. 



t In Curtis's Botanical Magazine, 1828, PI. 2826, Dr. Hooker has pub- 

 lished an Engraving of a Cycas circinalis which in 1827 flowered in the Bo- 

 tanic Garden at Edinburgh. See PI. 1. Fig. 33. 



t Copied from an engraving published by Mr. Lambert, of a plant that 

 bore fruit at Walton on Thames in the conservatory of Lady Tankerviile, 

 1832. 



§ Thg sketch, PI. 57, Fig, 2, represents a triple series of circular undula. 



