It is hardly necessary to assume that the same law of vital force governs in the appearance and geographical distribution of _fungi_, as universally obtains in the higher and more complex vegetal growths. And although it may be difficult, in some instances, to draw the precise line between certain low mycological forms and the amoeboid and some other primitive manifestations of animal life, yet all vegetable physiologists agree in assigning a purely vegetable origin to all the primary groups of fungi--their general cellular character determining their proper place in classification. And in all their extended family groups, pervading nature as widely as animal and vegetable life, we find that uniform chemical and other conditions produce uniform mycological results. Spores are no more necessary for their appearance, in the first instance, than acorns are essential to the appearance of an oak forest when it succeeds the pine. Wherever the necessary conditions of moisture and heat are found to obtain, in connection with decayed or decaying substances, the particular form of fungus indicated thereby, whether parasitic or non-parasitic, will make its appearance. Continuously damp walls, or wall-paper, will produce them in specific variety, not because their invisible spores are flying about in the atmosphere to find appropriate lodgment, but because the necessary conditions obtain for their manifestation, or for the development of their vital units--those everywhere diffused, and ready to burgeon forth from the proper matrix, or from certain nutrient conditions to be met with in all vegetable substances, after the process of decay has commenced. Some orders appear only in a single matrix, but the greater part of them flourish on different decaying substances.