Leaves of several different basil varieties: From left to right Mediterranean ("sweet") basil, African Blue, lemon basil (O. americanum), spice basil, Thai basil (Siam Queen) and tree basil (O. gratissimum), upper and lower sides. http://www-ang.kfunigraz.ac.at/~katzer/engl/generic_frame.html?Ocim_bas.html