1. _Foerstia._ These fossils may be the earliest known occurrence of
bryophytes, although some authors have referred them to
the brown algae. After Dawson.
2. _Psilophyton._ A primitive vascular plant. After Dawson.
3. _Lepidodendron._ After Hirmer.
4. _Sigillaria._ After Hirmer.
5. _Calamites._ After Hirmer.
6. _Sphenophyllum._ After Fuller and Tippo.
7. _Equisetum._ The only living genus of scouring rushes. After Fuller
and Tippo.
8. _Megaphyton._ An ancient true fern. After Hirmer.
9. Modern tropical tree fern. After Fuller and Tippo.
10. _Medullosa._ An ancient seed fern. After Stewart.
11. _Williamsonia._ An extinct cycad-like tree. After Sahni.
12. _Cycas._ A modern cycad. After Chamberlain.
13. _Baiera._ A fossil leaf genus of ginkgo, whose only living
representative is the species _Ginkgo biloba_, saved from
extinction by careful cultivation in China. Several
specimens of this “living fossil” were presented to this
country by the Chinese and are now flourishing on many
college campuses, including that of the University of
Illinois. After Mägdefrau.
14. _Cordaites._ After Grand Eury.
15. _Lebachia._ A “transition conifer,” forerunner of present day
conifers. After Mägdefrau.
16. _Pinus._ Modern pine. After Mägdefrau.
17. _Acer._ Common maple, an angiosperm whose leaves are also found
among Tertiary fossils. After Mägdefrau.
18. _Rosa._ The prairie rose, an angiosperm.
19. _Campsis._ Trumpet vine, an angiosperm.
[Illustration: _Geologic Time Chart_]
_Time Units_
_Era and Years_
CENOZOIC “Recent Life”
Pleistocene
Pliocene
Miocene
Oligocene
Eocene
Paleocene
MESOZOIC “Middle Life”
Cretaceous
70 million
herbaceous lycopods
Jurassic
25 million
yellow-green algae
selaginellids
Triassic
30 million
cycad-like plants
Equisetum
PALEOZOIC “Ancient Life”
Permian
25 million
transition conifers
pines, spruces, firs, etc.
Equisetites
Pennsylvanian
25 million
ferns related to modern families
bryophytes
Mississippian
30 million
seed ferns
calamites
cycads
Devonian
55 million
cordaites
sphenophyllids
ancient ferns
Silurian
40 million
psitopsids
Foerstia
Ordovician
80 million
red algae
green algae
Cambrian
80 million
PROTEROZOIC _and_ ARCHAEOZOIC ERAS
4½ billion years
blue-green algae
chemosynthetic bacteria?
NO CERTAIN FOSSILS KNOWN
_Plants_
Algae
yellow-green algae
brown algae
red algae
green algae
blue-green algae
Mosses
bryophytes
Foerstia
Vascular Plants
“Whisk Ferns”
psitopsids
Club-mosses
scale and seal trees
quillworts
herbaceous lycopods
Scouring Rushes, Horsetails
Equisetites
Equisetum
calamites
selaginellids
Ferns and Seed Plants
Ferns
ancient ferns
ferns related to modern families
Gymnosperms
Cycads
seed ferns
cycads
cycad-like plants
Ginkgo
Conifers
cordaites
transition conifers
pines, spruces, firs, etc.
Flowering Plants
_Field Book_
PENNSYLVANIAN PLANT FOSSILS OF ILLINOIS