The science of plant symbolism may, if we accept the views of Miss Marshall, a writer on the subject,[16] be classified into five divisions. These are, firstly, plants which are symbols, pure and simple, of the Great Unknown God, or Heaven Father; and embrace those, the form, colour, or other peculiarities of which led the priests, the early thinkers to the community, the medicine-men, magicians, and others, to associate them with ideas of the far-distant, unknown, incomprehensible, and overwhelming--the destructive forces of Nature. Such plants were used as hieroglyphics for these ideas, and became symbols of the Deity or Supreme Power. To these visible symbols belong plants such as the Lily, Onion, flowers of heavenly blue colour (symbolising the blue sky), and leaves threefold or triangular, symbolising God the Creator, Preserver, and Destroyer. [16] ‘Plant Symbolism,’ in ‘Natural History Notes,’ Vol. II. Secondly, the plants symbolising or suggesting portions or organs of the human body, internal and external, which to the earliest of mankind, and certainly to the Egyptian embalmers, were organs of mystery and importance; such is the heart, the first to beat in the fœtal, and the last to cease pulsating in the adult organism, &c. To this section belong heart-shaped leaves and petals; and where, as in the Shamrock, there is united the threefold emblem and the heart-shaped leaf, there is a doubly sacred idea united with the form. To this section belong also plants and fruits such as the Fig, Pomegranate, &c. The third section comprises plants that were consecrated or set apart as secret and sacred, because those who possessed the knowledge of their powers made use of them to awe the ignorant people of their race. These plants were supposed to be under the control of the good or evil powers. They were the narcotics, the stupefying or the exciting vegetable drugs. The sacred incense in all temples was compounded of these, and their use has been, and still is, common to all countries; and as some of these compounds produced extraordinary or deadly effects, as the very dust of the burnt incense, when mixed with water, and drunk, brought on a violent and agonising death, while the fumes might merely produce delightful and enticing ecstacy, making men and women eloquent and seemingly inspired, the knowledge was wisely kept secret from the people, and severe penalties--sometimes even death--awaited those who illegally imitated, compounded, or used these drugs. To this section belong the plants used to make the Chinese and Japanese joss, as well as Opium, Tobacco, Stramonium, and various opiates now well known.