FOSSIL CRYPTOGAMIA, 87 
of fossil leaves, fruits, and stems, whose characters and rela- 
tions are but imperfectly known ; as Carpolithes, Endogenites, 
&c. Upon these principles the present arrangement has 
been founded: the progress of discovery will, of course, be 
continually adding to the list, and the classification require 
to be modified. 
The following account of the principal types of the ancient 
floras whose relics are preserved in the mineral kingdom, 
though commencing with those of the most simple struc- 
ture, the Cryptogamia, and advancing to the higher orders, 
is not strictly botanical ; for it was found convenient, in 
some instances, to notice certain species and genera of diffe- 
rent orders under the same head, from their occurrence in 
the same geological formations. 
It is estimated that not more than two thousand spe- 
cies of plants have been discovered in a fossil state, while 
the known recent species amount to upwards of eighty 
thousand. 
CrLLuLaR Crrprocamia; Atc#.—The plants designated 
by botanists Algew, and commonly known as sea-weeds, 
lavers, and fresh-water mosses, are of the most simple 
structure—mere aggregations of cells—but present innume- 
rable varieties of form and magnitude: many species are 
mere vesicles of such minuteness as to be invisible to the 
unassisted eye, except accumulated in countless myriads, 
when they appear asa green, purple, or reddish, slime in the 
water ; or as a film on wood or stone, or on the ground, in 
damp situations ; while others are tough branched marine 
plants, many fathoms in length. 
The Algze form three principal groups: 1. the jointless, as 
the Fuci, the Dulses, Tangles, and Lavers: 2. the jointed, 
which are composed of thread-like articulated tubes ; such 
are the fresh-water Confervee: 3. the disjointed, or Brittle- 
worts, so called from their spontaneous self-division, which 
is in some kinds complete, in others only partial; and these, 
