...[T]here are few indeed except trained naturalists who realize that any but a quite casual and superficial relation exists between these woodland toadstools and the trees under which they appear, or have carried their observations a stage further and noted the regular coincidence of certain kinds with particular tree species.

The association between the toadstool-producing fungi of woodlands and our common trees is only one of many unlikely ways in which plants belonging to widely different groups are interrelated with one another and with the mechanism of life as a whole. Because this is...