Nice picture, too. I am pretty sure what I saw was sweetgum, but there
is still some doubt (especially since I am not likely to ever return.)
Both species present, but these seemed to have the larger, rounder,
pendant "things" up there. It is just that there were some sweetgum
with those corky wings on the twigs that were so obviously sweetgum.
These did not. Too bad I didn't have my camera. I did save a number of
oak leaves and pine cones. There were also magnolia and another tree
with similar shaped leaves, but much thinner and sort of gray-green on
the back -- definitely evergreen. The terminal bud was pointy but
nowhere near as big as magnolia. I can't find it in any of my tree
guides. Photos at : http://www.bcn.net/%7Ejohneich/treetops.html

Anyway, here is a list after all:

Callaway Gardens, near Pine Mountain, Georgia, in the area of the
Southern Pines Conference center. Most trees were in a cove above the
main swimming area of Chickadee Lake.

Tuliptree:
128.1'h, 10.8'c
118.4'h, 5.5'c
115.5'h, 13.1'c really nice tree
115.5'h, 9.7'c

"Sweetgum"
110.9'h, 5.0'c
116.2'h, 7.6'c
114.9'h, 6.0'c
119.4'h, 6.0'c
120.8'h, 4.5'c
126.2'h, 6.5'c balding bark to 6'h
123.2'h, 6.6'c
112.5'h, 3.2'c high h/d ratio

Magnolia Grandiflora
64.9'h, 3.8'c
71.0'h, 4.0'c
84.5'h, 5.4'c

Southern Red Oak
102.0'h, 4.2'c
100.7'h, 5.1'c
100.8'h, 4.0'c

White Oak
95.5'h, 4.1'c
108.5'h, 5.0'c

Either Longleaf or Loblolly Pine (?) I think both were present, this
was the tallest pine there.
124.6'h, 7.5'c

The following oaks were different species, but I was guessing by the
leaves at the base.

Water Oak (?)
101.7'h, 5.5'c
95.3'h,
111.3'h, 5.0'h

??? Oak #1 Whitish blocky bark like white oak up here (not like the
white oak there, though, which was shaggy above like a shagbark hickory.)
112.6'h, 6.9'c
116.6'h, 6.3'c
121.2'h, 5.2'c

??? Oak #2 Very dark bark, almost black, similar to northern red oak in
texture
100.7'h,   5.1'c

Laurel-like leaves, glossy, non-serrated, 6"x2", alternate, pointy brown
terminal bud, gray bark like beech tree, can't find in book.
99.7'h, 4.0'c

Hey, that is enough "species" to calculate a Rucker index: 110.7. I
may not know what they are, but they are different species.

John