Under oak.
Alonso says this is Scleroderma citrinum due to the reticulate spores. He also says that he has never seen this species under oak before.
Spore statistics (measurements do not include the reticulation)
10.1 [11.5 ; 12.4] 13.7 × 9.7 [10.8 ; 11.5] 12.5 µm
Q = [1 ; 1.1] 1.2 ; N = 15 ; C = 95%
Me = 11.9 × 11.1 µm ; Qe = 1.1
12.83 12.44
10.86 10.43
11.37 11.22
10.36 10.28
12.54 11.86
12.03 11.40
12.37 10.93
10.65 10.07
12.92 11.98
10.70 10.65
12.91 11.30
12.38 11.78
12.35 10.08
11.76 10.90
12.69 11.52