KEEPING WARM 
Larry Stone 
Above: Snow trillium's bright white 
petals may make it more visible to 
pollinators. Some insects seem 
content to bask in warm flowers 
without feeding. Left: This marsh 
marigold is truly an early bloomer. 
Once the flower is free of the ice, 
its petals, shaped like a shallow 
bowl, may help accumulate heat from 
the low spring sun. 
directly at the sun. Using small thermis- 
tors, I attempted to measure tempera- 
ture differences between centers of the 
trillium flowers and the surrounding air. 
When the sun was out, the temperature 
in the flower centers was consistently 4 
to 5 degrees warmer than the air; the 
difference gradually disappeared when 
the flowers were shaded or when a cloud 
passed over the sun. Several other early 
bloomers, such as the hepaticas ( Hepat - 
ica spp.) and the anemones ( Anemone 
spp.) are less accurate sun followers, but 
they have a shallow-dish shape, as well 
as the extremely shiny upper petal sur- 
faces characteristic of the buttercup 
family. Unfortunately, the anemones 
and hepaticas were too small for me to 
take their temperatures accurately with 
the equipment I had. 
The largest early-blooming flower I 
was able to examine was. not a forest 
plant, but the prairie pasqueflower 
(. Anemone patens). Its flowers, which 
have a deep-dish shape, are as much as 
1.5 to 2 inches across, follow the sun 
closely, and contain almost innumerable 
fuzzy stamens and carpels in their cen- 
ters. The temperature of the first flower 
center I examined was an exciting 18 
degrees above the near-freezing air of an 
April morning. When the air was still 
and the sun constant, most of the 
pasqueflower blooms I measured were 
from 14 to 18 degrees warmer than their 
surroundings, and like the trilliums, 
these flowers returned to near-ambient 
temperatures when shaded for a time. 
Small bees, beetles, or other flying in- 
sects were always present in the 
pasqueflowers. Insects frequently spent 
the night in the blossoms, which closed 
with darkness, and even w hen skies were 
overcast, many remained completely 
stationary in the flow ers for long periods 
of time. Very little nectar is present in 
pasqueflower blooms, and while pollen 
is abundant, few insects were observed 
feeding on it or earning it away with 
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