Data Views Total Plants: 31 Show all rows. Paginate rows. Click on column headings to sort table by that column Plant Part All parts ... Essential Oil Leaf Plant Low PPM High PPM StdDev *Reference *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.