370 INTERMEDIATE CHARACTER OF CYCADEiE. 



The Cycadese form a beautiful family of plants whose 

 external habit resembles that of Palms, whilst their internal 

 structure approximates in several essential characters to that 

 of Coniferae. In a third respect, (viz. the Gyrate Vernation, 

 or mode in which the leaves are curled up at their points, 

 within the buds,) they resemble Ferns. (See PI. 1. F. 33,. 

 34, 35, and PL 58, 59.) 



I shall select the family of Cycadeae from the fossil Flora 

 of the Secondary period, and shall enter into some details 

 respecting its organization, with a view of showing an 

 example of the method of analysis, by which Geologists are 

 enabled to arrive at information as to the structure and 

 economy of extinct species of fossil vegetables, and of the 

 importance of the conclusions they are enabled to establish. 

 Those who have attended to the recent progress of vegeta- 

 ble Physiology will duly appreciate the value of microscopic 

 investigations, which enable us to identify the structure of 

 vegetables of such remote antiquity, with that which pre- 

 vails in the organization of living species. 



The physiological discoveries that have lately been made 

 with respect to living species of Cycadeae, have shown 

 them to occupy an intermediate place between Palms^ 

 Ferns, and Coniferac, to each of which they bear certain 

 points of resemblance ; and hence a peculiar interest attends 



The most abundant deposit of fossil leaves of Cycadese in England, is in 

 the Oolitic formation on the coast of Yorkshire, between Whitby and Scar- 

 borough, (See Phillips' Illustration of the Geology of Yorkshire.) Leaves of 

 this family occur also in the Oolitic slate of Stonesfield. Lindley and Hut- 

 ton, Foss. Flora, PI. 172, 175, 



In Lindlcy and Hutton's Fossil Flora, PI. 136, Figures are given of Cones 

 which he refers to the genus Zaniia, from tlic sand-stone of the Wcaldcn 

 formation at Yaverland on the South coast of the I. of Wight. 



M. Ad. Brongniart has established a new fossil genus Nilsonia, in the 

 family of Cycadca), which occurs at Hoer in Scania, in strata, either of the 

 Wealden or Grccn-sand formation ; and another genus, Pterophyllum, 

 which is found from the New red sand-stone upwards to the Wealden for-- 

 mation. 



