As rudimentary organs vary much, we can thus also probably understand the variability, which Dr. Hooker informs me is characteristic of the excrescences on the labellum. In some Orchids which have a spur-like nectary, the two sides are apparently formed by the two modified stamens; thus in Gymnadenia conopsea (but not in Orchis pyramidalis), the vessels, proceeding from the antero-lateral ovarian group, run down the sides of the nectary; those from the anterior group run down the exact middle of the nectary, then returning up the opposite side form the mid-rib of the labellum. The extension of these lateral elements of the nectary apparently explains the tendency, as in Calanthe, Orchis morio, etc, to the bifurcation of its extremity.
The number, position, and course of the spiral vessels exhibited in the diagram (Fig. XXXII.), were observed in some Vandeæ and Epidendreæ.[1] In the Malaxee all were observed excepting a 3, which is the most difficult of all to trace, and which apparently is oftenest absent. In the Cypripedee, again, all were traced except a3, [2] which, I feel pretty sure, was here really absent: in this tribe the stamen (A1) is represented by a conspicuous shield-like rudiment, and a l and a2 are developed into two fertile anthers. In the Ophreæ and Neotteæ all were traced, with the important exception of the vessels belonging to the three stamens (a 1, a2, and a3) of the inner whorl. In Cephalanthera grandiflora, however, I clearly saw a 3 proceeding from the anterior ovarian group, and running up the front of the column: this anomalous member of the Neottee has no rostellum, and the vessel marked Sr in the diagram was entirely absent, though seen in every other Orchid.
- ↑ 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 bifurcating, and sending a group (a3) 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 clinandrum. 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 (a3) 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 Sr to the viscid gland of the pollinium. In the Epidendrea I traced all the vessels in a Cattleya; and all in Evelyna carivata except a3, which I did not search for. In the Malaxee I traced all in Liparis pendula except a3, 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 a3, 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 a2, which were certainly absent. In Epipactis I traced all excepting a 1, a2, and a3, which are certainly absent. In Spiranthes autumnalis the vessel Sr 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 Ophrea do the vessels a l, a2, and a3 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 Sr, 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 of course the three of the inner staminal whorl, and I looked carefully for a3: the vessel supplying the fertile anther runs up the connective membrane between the two anther-cells, but does not bifurcate: the vessel to the rostellum runs up to the top of the shoulder or ledge beneath the connective membrane of the anther, but does not bifurcate and extend to the two widely-separated viscid discs.
- ↑ From Irmisch's ('Beitrige zur Biologie der Orchideen,' 1853, s. 78 and 42) description of the development of the flower-bud of Cypripedium, it would appear that there is a tendency to the formation of a free filament in front of the labellum, as in the case of Glossodia before mentioned; and this will perhaps account for the absence of spiral vessels, proceeding from the anterior ovarian group, and coalescing with the column. In Uropedium, a genus which A. Brongniart ('Annal. des. Sc. Nat.,' 3rd series, Bot. tom. xiii. P. 114) considers closely allied to, and even perhaps a monstrosity of, Cypripedium, a third fertile anther occupies this same exact position.
