All the known facts on
this head have been collected by Delpino in his 'Ult. Osserv.' part 2
fasc. 2 1875 pages 59-63.)
The amount of pollen produced by anemophilous plants, and the distance
to which it is often transported by the wind, are both surprisingly
great. Mr. Hassall found that the weight of pollen produced by a single
plant of the Bulrush (Typha) was 144 grains. Bucketfuls of pollen,
chiefly of Coniferae and Gramineae, have been swept off the decks of
vessels near the North American shore; and Mr. Riley has seen the ground
near St. Louis, in Missouri, covered with pollen, as if sprinkled with
sulphur; and there was good reason to believe that this had been
transported from the pine-forests at least 400 miles to the south.
Kerner has seen the snow-fields on the higher Alps similarly dusted; and
Mr. Blackley found numerous pollen-grains, in one instance 1200,
adhering to sticky slides, which were sent up to a height of from 500 to
1000 feet by means of a kite, and then uncovered by a special mechanism.
It is remarkable that in these experiments there were on an average
nineteen times as many pollen-grains in the atmosphere at the higher
than at the lower levels. (10/54. For Mr. Hassall's observations see
'Annals and Magazine of Natural History' volume 8 1842 page 108. In the
'North American Journal of Science' January 1842, there is an account of
the pollen swept off the decks of a vessel.
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