Take note that some of the simples are obtained from minerals, others from plants, and others from animals. Simples obtained from minerals: emerald, sapphire, pearl, and the like are such. Simples indeed obtained from plants: leaves, seeds, roots, stems, blossoms, fruit, and grain are such. Note particularly that it is proper to use the leaves when they begin to have their proper size in full and when they survive in their own shape without change of color and without falling. It is indeed proper to gather the seeds when their size is complete, and when their natural condition and viscidity are seasoned. It is indeed proper to gather the roots when the foliage falls. It is indeed proper to gather the fruit before they fall or before they are ready to fall, when they have reached maturity, because they ought to be gathered in the prime of their strength.