Data Views Total Plants: 2 CSV Excel PDF Click on column headings to sort table by that column Plant Part All Leaf Leaf Essent. Oil Low PPM High PPM StdDev *Reference Agathosma betulina Leaf Essent. Oil -- -- * Mentha x rotundifolia Leaf -- -- Jim Duke's personal files. *Unless otherwise noted all references are to Duke, James A. 1992. Handbook of phytochemical constituents of GRAS herbs and other economic plants. Boca Raton, FL. CRC Press.