Pliny had long ago beautifully said that "blossoms are the joy of trees, in bearing which they assume a new aspect, vyeing with each other in the luxuriance and variety of their colours." Linnæus has justly applied this to plants in general, and, improving upon the idea, he considers their herbage as only a mask or clothing, by no means indicative of their true nature or character, which can be learned from the flower and fruit alone.
Mr. Knight has traced his central vessels, by which the sap is conveyed from the root, into the flower and fruit. On the returning sap in the bark of these parts he has not been able to make any distinct observation; but he has determined that no matter of increase is furnished from the flowers or their stalks, as from leaves, to the part of the branch below them, nor indeed to any other part, Phil. Trans. for 1801, p. 340. There can be no doubt that certain parts of the flower, which we shall presently describe, perform functions respecting air and light analogous to those of leave, but entirely subservient to the benefit of the flower and fruit. Their secretions, formed
