its purchase for the park in 1928. The old-growth forestlands throughout Green Lakes State Park were extensively surveyed in 2001-2002 by members of the Wildwood Ancient Forest Alliance. The surveys found that there are about of old-growth forest within the park. The surveyors speculated that the paucity of hemlock trees in some areas indicates selective cutting of this species, perhaps for log roads in the mid 19th Century. They nonetheless conclude that "Green Lakes State Park is likely the finest old growth forest in central New York." Green Lakes State Park contains particularly old and large examples of tuliptrees, sugar maples, beech, basswood, hemlocks, and white cedars. One particularly impressive grove of trees, lying just southwest of Round Lake, was renamed the Tuliptree Cathedral following the 2001-2002 old-growth surveys. A survey of the heights of especially large trees was reported in 2011; the tallest was . Limnology of Round Lake and Green Lake The lake is deep, which is remarkable given its diameter of . Both Round Lake and Green Lake are meromictic, which means that the bottom waters of the lake are not mixed annually with the surface waters. For both lakes, the waters deeper than are unmixed and essentially devoid of oxygen. Meromictic lakes are quite rare; nearly all lakes undergo mixing of their deep and shallow waters at least once each year. Green Lake in particular has been the subject of a great deal of limnological research. The lakes are meromictic both because of their depth (relative to their diameters) and because there is an influx of mineral-laden groundwater into them; to some extent the lakes are giant mineral springs. The mineral content also accounts for the lakes' greenish appearance at certain times of year, when small particles of calcium carbonate and other minerals precipitate out of the water; these "whitings" cause the white coating of the lake bottoms that is readily observable at the shoreline. In addition to the strictly limnological research on the lakes, the sediments at their bottoms are being used to explore the history of the plant and animal life and of the climate around the lake over the last several thousand years (i.e. its paleoclimatology). Because the deep, oxygen-depleted bottoms of the lakes are undisturbed either by annual mixing or by "bioturbation" (plant growth or movement of worms and other animals), each year's sediments are preserved as distinguishable layers (or varves) that