102 THE OPEN BOOK OF NATURE 
impressions of some ferns strangely like some 
modern species. 
Generally speaking, the fossils of Permian plants 
resemble those of the Carboniferous Period. They 
include remains of club-mosses, horse-tails, and 
Sigillarie, but the quantity and variety are less. 
Tree-ferns flourished in Permian times. Cone- 
bearing plants, like the fir, were common then, 
and it is in Permian rocks that are found the 
earliest traces of cycads (Greek, kykas=the doom- 
palm), which are fernlike plants having short 
branchless stems marked with scars of fallen 
leaves. The leaves are all clustered at the sum- 
mit of the stem, and uncurl themselves like fern- 
fronds. 
The coal-seams and shales of the Triassic Period 
yield relics of ferns, horse-tails, cone-bearing plants, 
and cycads, the last-mentioned showing an increase 
on the Carboniferous cycads, both as to quantity 
and species. 
Cycads still flourished in Jurassic times, and very 
distant ancestors of our Araucarias (‘‘ Monkey- 
puzzles ’’) existed in that period. 
The Cretaceous rocks show an interesting develop- 
ment of plant-life. The lowest Cretaceous strata 
yield plant remains very similar to those found in 
Jurassic rocks ; but higher beds of later deposition 
contain remains of vegetation strikingly like that 
of modern times. In addition to remains of 
palms, cycads, pines, and many ferns, we find 
abundant traces of familiar trees, such as poplars, 
oaks, walnuts, figs, beeches, buckthorns, and. 
planes. And from Cretaceous times the vegeta- 
