Page:Darwin - The various contrivances by which orchids are fertilized by insects (1877).djvu/259

. VIII. as in Calanthe, Orchis mono, &c., to the bifurcation of its extremity.

The number, position, and course of all the spiral vessels exhibited in the diagram (fig. 36) were observed in some Vandeæ and Epidendreæ.It may be advisable to give a few details on the flowers which I dissected; but I looked to special points, such as the course of the vessels in the labellum, in many cases not worth here giving. In the Vandeæ I traced all the vessels in Catasetum tridentatum and saccatum; the great group of vessels going to the rostellum separate (as likewise in Mormodes) from the posterior ovarian group, beneath the bifurcation supplying the upper sepal and fertile anther; the anterior ovarian group runs a little way along the labellum before it bifurcates and sends a group (a$3$) up the front of the column; the vessels proceeding from the postero-lateral group run up the back of the column, on each side of those running to the fertile anther, and do not go to the edges of the clinandrun. In Acropera luteola the base of the column, where the labellum is attached, is much produced, and the vessels of the whole anterior ovarian group are similarly produced; those (a$3$) going up the front of the column are abruptly reflected back; the vessels at the point of reflexion are curiously hardened, flattened, and produced into odd crests and points. In an Oncidium I traced the vessels S$r$ to the viscid gland of the pollinium. Among the Epidendreæ I traced all the vessels in a Cattleya; and all in Evelyna carivata except a$3$, which I did not search for. In the Malaxeæ I traced all in Liparis pendula except a$3$, which I do not believe is present. In Malaxis paludosa I traced nearly all the vessels. In Cypripedium barbatum and purpuratum I traced all except a$3$, which I am nearly sure does not exist. In the Neotteæ I traced in Cephalanthera grandiflora all the vessels, excepting that to the aborted rostellum and those to the two auricles a$1$ and a$2$, which were certainly absent. In Epipactis I traced all excepting a$1$, a$2$, and a$3$, which are certainly absent. In Spiranthes autumnalis the vessel S$r$ runs to the bottom of the fork of the rostellum: there are no vessels to the membranes of the clinandrum in this Orchid nor in Goodyera. In none of the Ophreæ do the vessels a$1$, a$2$, and a$3$ occur. In Orchis pyramidalis I traced all the others, including two to the two separate stigmas: in this species the contrast between the vessels of the labellum and of the other sepals and petals is striking, as in the latter the vessels do not branch, whilst the labellum has three vessels the lateral ones running of course into the antero-lateral ovarian group. In Gymnadenia conopsea I traced all the vessels; but I am not sure whether the vessels supplying the sides of the upper sepal do not, as in the allied Habenaria, wander from their proper course and enter the postero-lateral ovarian group: the vessel S$r$, going to the rostellum, enters the little folded crest of membrane, which projects between the bases of the anther-cells. Lastly, in Habenaria chlorantha I traced all the vessels, excepting as in the other Ophreæ the three of the inner staminal whorl, and I looked carefully for a$3$: the vessel In the Malaxeæ