58 THE MEDALS OF CREATION. - CHap. IV. ‘ 
have above stated, consists of elongated cells or tubes, of — 
two kinds: in the one, the membrane of which they are com- — 
posed is smooth: in the other, the walls of the tubes are — 
covered by little oval or circular bodies called glands (Lign. 
1, fig. 1, ¢.). A branch of larch or pine, split longitudinally, 
and viewed by a powerful lens, will exhibit the appearance 
here described. This glandular structure is so constantly 
and largely developed in the conifers, that although it is 
also possessed by other aromatic trees, we shall rarely err in 
referring fossil wood in which this organization is apparent, 
to this family of vegetables (see Plate V. figs. 2, 3). These 
glands in the pines and firs, are supposed to be the cells 
which secrete a colourless volatile oil, that exudes in the 
state of turpentine. 
From this general account of the vegetable structures 
that may be expected to occur in the mineral kingdom, the 
student will in some measure be prepared for the investi- 
gation of fossil trees and plants; but for the guidance of 
those who are wholly unacquainted with the principles on 
which the Natural System of Botany adopted in this work, 
is founded, I am induced to present the following concise 
view of the principal divisions of the vegetable kingdom, 
though it involves some repetition. 
The following summary is given nearly in Dr. Lindley’s 
own language :— 
Botanical PrincipLes.—One of the first things that 
strikes an inquirer into the structure of plants, is the fact, 
that while all species are capable of propagating their race, 
the mode in which this function is effected is essentially 
different in different cases. In most tribes of plants, flowers 
are produced, and these are succeeded by fruit, containing 
seed, which is shed, or scattered abroad, and grows into new 
individuals. But in certain families (the Cryptogamia), as 
Ferns, Mosses, Mushrooms, and the like, neither flowers, nor 
seeds properly so called, have been detected ; but propaga- 
