[38] Nieuwland: Notes on our local flora. Amer. Mid. Nat. Vol. 3:230:1914.
[39] Michaux: North American Silva. J. J. Smith's Trans. Vol. 1:37:1871.
[40] Nieuwland: Notes on our local flora. Amer. Mid. Nat. Vol. 3:230:1914.
[41] Prof. B. Shimek told me that recently a few trees were found about 30 miles west of Iowa City, Iowa.
[42] Sargent: Notes on North American Trees. Bot. Gaz. Vol. 65:424:1918.
[43] Brown: Trees of Fountain County, Ind. Geol. Rept. Vol. 11:123:1882.
[44] Sargent: Notes on North American Trees. Bot. Gaz. Vol. 65:427:1918.
[45] Bot. Gaz. Vol. 67:217-229:1919.
[46] Hill: Notes on Celtis pumila, etc. Bul. Torrey Club: Vol:27:496-505:1900.
[47] Bot. Gaz. Vol. 67:228-229:1919.