Archaeology Magazine - March 1962 - 17

are seldom encountered in sediments less than sixty
million years old (the geologically young strata!).
Fossilized pollen grains, especially of angiosperms,
are dominant only in the younger strata, and probably
reflect the recent evolution of this group of plants,
which now forms most of the world's vegetation.

Post who achieved the full potential of the method.
He found that by assembling data on the kind and
number of grains from samples at different stratigraphic levels in bogs, the history of climatic change
could be determined more sensitively than by the use
of plant fragments preserved in the bogs.
Previously the importance of quantitative data had
not
been fully appreciated; only the occurrence and
The wind-pollinated
(anemophilous) plants prodistribution
of pollen types had been noted. Since
duce enormously greater amounts of pollen than the
frewhich
frequency analysis is the basis of all modern pollen
animal-pollinated (zoöphilous) plants,
von Post's discovery was of the greatest imwork,
are
to
a
quently
adapted
pollination by
particular
animal. Thus most of the pollen preserved in sedi- portance. This work was preceded by about 250 years
of pollen study, most of it descriptive. The foundaments was wind-borne.
tion
for modern pollen morphology was laid largely
the
are
all
conifers
Among
wind-pollinated plants
and many hardwood trees and herbaceous plants. The by the nineteenth-century German scientists Fritzsche,
spores of free-sporing plants are also wind-borne. von Mohl and Fischer, as well as by the seventeenthAlthough insect-pollination prevails among angio- century microscopists Malpighi and Grew. Fossil
sperms as a whole, the world's major vegetation types microspores observed in ancient sediments in the
- forest and grassland- are almost
wholly wind- 1830's and in subsequent years were treated more or
less as palaeobotanical curiosities.
outside
the
pollinated, especially
tropics.
Thousands of years ago pollen and plant fertilizaSeveral years ago the German scientist Pohl published some interesting figures on pollen production, tion played a part in the life of peoples who had no
based both on careful calculations and on estimates. idea of pollen's microscopic appearance or its sciPine, for example, may produce 1,500,000 grains per entific value. For example, the Assyrians, around
male cone, juniper 400,000, oak 41,000 per tassel, 885 b.c., depicted the symbolic fertilization of the
maple 8000 per flower. Differences in absolute pollen date palm in a series of sun-baked brick mural reproduction must be considered in interpreting differ- liefs. Since the date palm provided "food and drink,
ences in fossil pollen frequencies. Some genera with shelter and furniture, and materials for his crafts,"
abundant pollen are naturally over-represented in (J. B. Stearns and D. P. Hansen, The Assyrian Reliefs t
sediments, while others with sparse pollen production at Dartmouth [Dartmouth, 1953] page 3) the Assyrians practised hand-pollination to insure fertility and
leave an inadequate picture of their abundance.
Pollen output may also be expressed as the total superior yields. Thus they recognized sexuality in
pollen productivity of a forest, or as total counts of plants nearly three thousand years before it was undeposited pollen. The spruce forests of Sweden are derstood to the satisfaction of modern biologists.
said to produce 75,000 tons of pollen annually- about
1,000,000,000,000,000,000,000 or 1021 grains. In The success of fossil pollen research depends on a
Britain the aerobiologist Hyde records pollen settling fortunate combination of features: first, most
pollen
at the rate of 5000 grains per square centimeter per and spores possess a stable, chemicallyinert outer wall
year, which would amount to something on the order (exine) which resists deterioration and the action of
of 50-100 grains per cubic millimeter of accumulating chemical reagents necessaryto extract it from the rock
sediment.
matrix; second, the exine has diagnostic features
which are inherited, so that pollen and spores, at
Current pollen research is built on discoveries least for the last sixty million years of earth history,
made in the early nineteen hundreds, when Swedish can be linked taxonomicallywith living genera. Pollen
scientists were pioneers in the study of bog stratig- of alder or birch, for instance, can be traced back for
raphy. The discovery of plant fragments (such as tree millions of years without appreciable change.
For pollen identification, analysts rely upon certain
trunks, seeds and pine cones) in various bog levels
enabled them to reconstruct the vegetation and climate observable features: apertures (kind, number, arof Sweden since the last glaciation. The splendid rangement and structural modifications), sculpture
preservation of fossil pollen among the other plant pattern (surface design) and wall structure. The
remains in the peat stimulated the imagination of apertures consist of pores and furrows (colpi); these
the botanist H. G. Lagerheim and the young geologist may be breaks in the exine, but are usually places
Lennart von Post, his student. Although Lagerheim where the exine is thinned and structurally modified.
laid the groundwork in pollen analysis, it was von The pore is typically round ; the furrow is usually long
17

Archaeology Magazine - March 1962

Table of Contents for the Digital Edition of Archaeology Magazine - March 1962