This section is from the book "The Gardener's Monthly And Horticulturist V20", by Thomas Meehan. See also: Four-Season Harvest: Organic Vegetables from Your Home Garden All Year Long.
Formed in summer on the underside of the leaves of Quercus obtusiloba, Q. macrocarpa, and Q. alba, often to the number of 1,000 on a single leaf: each gall inserted in a deep cavity which causes, on the upper surface, a bulging of a straw-yellow color, irregularly sub-conical, with the top flat-tened or concave, and with a minute central nipple, sometimes obsolete; the galls becoming detached and falling to the ground in autumn, leaving a pale, fulvous, circular disc at the bottom of the; cavity. The gall has an average diameter of 1 mm., and the color and general appearance of a miniature acorn - the base being paler than the sides and conically produced to the central point of attachment. The apical portion is slightly constricted into a deep purple-brown rim, and the top within this rim is flat, with a small central nipple.
Received at different times from M. W. Harrington, of Ann Arbor, Mich.; from Irvin Armstrong, of Vevay, Ind.; from N. B. Baldwin, of Elgin, Ills., and from Win. R. Howard, of Forsyth, Mo.; also sufficiently common in St. Louis county.