There remains in this department of inquiry only one additional set of facts, to which reference may be made, as illustrating _distribution of work among insects and birds_, assigning them to different orders of plants. This will illustrate contrivance on a still wider scale, discovering distinct sets of affinity, which imply common localization for given plants and animals. In this it appears that flies, humble bees, and birds with long slender bills, such as the humming birds, all have a share in the work required for fertilizing plants. There is one example, _epipactis latifolia_, with a cup-shaped labellum, in which honey is secreted, and which bees are never seen to frequent. What, however, the bees pass, the wasps suck eagerly, and by them it is fertilized. Of this flower, Mr. Darwin says,--"It is very remarkable that the sweet nectar of this _epipactis_ should not be attractive to any kind of bee. If wasps were to become extinct in any district, so probably would the _Epipactis Latifolia_."[BX] Another example there is of an orchid _(Spiranthes Autumnalis_), commonly known as _Ladies' Tresses_, having a series of spikes, of which the lowest flowers are first matured, the others following in order as they rise towards the summit. This plant is frequented by bees, whose practice it is to begin with the lowest flowers and ascend gradually to the top. This order in seeking to extract the honey, proves to be the proper one for fertilizing of the plant, because the pollen which the bee brings will be received by the riper flower on which it lands, and when that has been deposited, fresh pollen will adhere to the bee as it rises to the less matured flowers, and thus it departs laden with pollen destined for the lowest flowers of the next plant it visits.[BY] [Illustration: 1 SECTION OF ORCHID FLOWER SHOWING POLLEN VESSEL, SEED STORE AND HONEY STORE 2 BEE ENTERING 3 POLLEN VESSEL 4 BEE RETREATING 5 BEE PREPARED FOR ENTERING ANOTHER FLOWER]