16 
INTERPRETATION OF FOSSIL PLANTS 
such is preserved in fossil resins, or as carbonized, silicified or 
calcified fragments, much can be learned of the physical condi¬ 
tions under which they lived. Something may also be learned 
from the arrangement of the stomata, their position, and the out¬ 
lines of the epidermal cells shown in cuticles of leaves preserved 
as impressions, which can frequently be recovered by appropriate 
methods. If the stomata are abundant and delicate, not sunken 
beneath the surface or with the elaboration of accessory cells they 
indicate abundant humidity and a plentiful water supply, with 
shade or not excessive insolation. If they are restricted to special 
regions of the leaf, or are sunken in grooves, as in Torreya, Pseu- 
docycas, or Lepidodendron, they indicate actual or physiological 
shortage of water, as does also the development of waxy or to- 
mentose surfaces, or thick palisade tissue. Lacunate roots, as in 
the Paleozoic Calamites; the formation of pneumatophores as in 
Rhizophora and Taxodium, or the development of a horizontal 
root-system, as in Taxodium and Stigmaria, indicate a marshy or 
swampy substratum, and growth where the ground water-table is 
at or above the surface of the ground. Enlargement of the base 
of the bole as in Nyssa and Taxodium, also is indicative of poor 
aeration and a wet substratum. In tropical angiosperms resins 
or gums are also frequently developed and aid in retarding evap¬ 
oration. 
Abundant coniferous remains of modern types indicate unfavor¬ 
able edaphic conditions. Abundant ferns indicate great humidity, 
as in the flora of the Kootenai formation (Early Cretacic) or that 
of the Late Cretacic Atane beds of western Greenland. Well 
distributed and heavy rains with high humidity and consequent 
cloudiness result in equable climates even in high latitudes, and 
bring into existence a type of vegetation like that of existing tem¬ 
perate rain forests (New Zealand, southern Chile) where the 
vegetation shows a mixing of botanical types and simulates that 
of warmer climates. The Late Cretacic floras of the Atlantic 
Coastal Plain clearly indicate conditions comparable to those of 
modern temperate rain forests. 
It is believed that in the past such oceanic climates resulted in a 
floral facies which paleobotanists have been inclined to interpret 
as indicative of tropical climatic conditions. One caution in at¬ 
tempting to deduce past climatic conditions may be stated, since 
