Page:Darwin - The various contrivances by which orchids are fertilized by insects (1877).djvu/79

. II. accordance with the belief of Linnæus, who grouped, them all together under the name of Ophrys insectifera. Mr. Moggridge further shows that in Italy O. aranifera flowers first, and O. apifera last, the intermediate forms at intermediate periods; and according to Mr. Oxenden, the same fact holds good to a certain extent in Kent. The three forms which inhabit England do not seem to blend into one another as in Italy, and I am assured by Mr. Oxenden, who has closely attended to these plants in their native homes, that O. aranifera and apifera always grow in distinct spots. The case therefore is an interesting one, as here we have forms which may be and generally have been ranked as true species, but which in North Italy have not as yet been fully differentiated. The case is all the more interesting, as the intermediate forms can hardly be due to the crossing of O. aranifera with apifera; this latter species being regularly self-fertilised and apparently never visited by insects. Whether we rank the several forms of Ophrys as closely allied species or as mere varieties of the same species, it is remarkable that they should differ in a character of such physiological importances as the flowers of some being plainly adapted for self-fertilisation, whilst the flowers of others are strictly adapted for cross-fertilisation, being utterly sterile if not visited by insects.

Herminium monorchis.—The Musk Orchis, which is a rare British plant, is generally spoken of as having naked glands or discs, but this is not strictly correct. The disc is of unusual size, nearly equalling the mass of pollen-grains: it is subtriangular, with one side protuberant, and somewhat resembles a distorted helmet in shape: it is formed of hard tissue with the base hollowed out, and viscid; the base resting on and being covered by a narrow strip of membrane, which is