Page:On the Various Contrivances by Which British and Foreign Orchids are Fertilised by Insects, and on the Good Effects of Intercrossing.djvu/21

 pollinium would be brought in front of an insect's head ready to strike the stigma. When a pollen-mass is placed on the stigma and then withdrawn, the elastic threads by which the packets are tied together, break, and leave several packets on the viscid surface. In all other Orchids the meaning of these several contrivances—namely, the downward movement of the lip of the rostellum when gently pushed the viscidity of the disc—the act of depression of the caudicle after the disc has been removed—the rupturing of the elastic threads by the viscidity of the stigma, so that the pollen may be left on several stigmas is unmistakably clear. Are we to believe that these contrivances in the Bee Ophrys are absolutely purposeless, as would certainly be the case if this species is perpetually self-fertilised? If the discs had been small or only viscid in a slight degree, if the other related contrivances had been imperfect in any degree, we might have concluded that they had begun to abort; that Nature, if I may use the expression, seeing that the Fly and Spider Ophrys were imperfectly fertilised and produced few seed-capsules, had changed her plan and effected complete and perpetual self-fertilisation, in order that more seed might be produced.

The case is perplexing in an unparalleled degree, for in the same flower we apparently have elaborate contrivances for directly opposed objects.

We have already seen many curious structures and movements, as in Orchis pyramidalis, which evidently lead to the fertilisation of one flower by the pollen of another flower, and we shall meet with numerous other and very different contrivances for the same object throughout the whole great Orchidean Family. Hence it is impossible to doubt that some great good is derived from the union of two distinct flowers, often borne on distinct plants; but the good in the case of the Fly and Spider Ophrys is gained at the expense of much lessened fertility. In the Bee Ophrys great fertility is gained at the expense if apparently perpetual self-fertilisation; but the contrivances are still present which are assuredly adapted to give an occasional cross with another individual; and the safest conclusion, as it seems to me, is, that under certain unknown circumstances, and perhaps at very long intervals of time, one individual of the Bee Ophrys is crossed by another. Thus the generative functions of this plant would be brought into harmony with those of other Orchidacæ, and, indeed, with those of all other plants, as far as I have been able to make out their structure.

Ophrys arachnites

This form is considered by some high botanical authorities as a mere variety of the varying Bee Ophrys. Mr. Oxenden sent me two spikes bearing seven flowers. The anther-cells do not stand so high above the stigma, and do not overhang it so much, as in the Bee Ophrys. The mass of pollen-grains is generally more elongated. The upper part of the caudicle is curved forward, and the lower part undergoes the movement of depression, as in the Spider and Bee Ophrys. The caudicle in length compared with that of the Bee Ophrys is only as two to three, or even as two to four; though thus relatively shorter, it is as thick and broad as that of the Bee Ophrys: it is much more rigid, so that, when the upper end of the pollinium is forced out of its anther-cell, the sticky disc remaining in the pouch, it can only with difficulty be bent down to the stigma. We here see no adaptation for self-fertilisation. The seven flowers sent me had evidently long been fully expanded, and the spikes, having travelled by railway, must have been well shaken, yet in six of the flowers both pollinia remained in their anther-cells; in the seventh, both pollinia adhered to the stigma with their discs still in their pouches; but this flower was much withered, and might have been crushed. Of the six flowers, three were so old that the pollen was mouldy and the petals discoloured; yet, as just stated, the pollinia were still in their cells. After having examined so many hundred flowers of the Bee Ophrys, I have never seen such a case. Considering this important functional difference in O. apifera and arachnites, and the lesser differences in the structure of their pollinia, which are likewise of functional signification, and the slight differences in their flowers, it seems to me that, until these forms can be shown to be connected by intermediate varieties, we must rank O. arachnites as a good species, more closely allied to O. aranifera in its manner of fertilisation than to O. apifera.

Herminium monorchis. The Musk Orchis is generally spoken of as having naked glands or discs, but this is not strictly correct. The disc is of unparalleled size, nearly equalling the mass of pollen-grains: it is subtriangular in shape, unsymmetrical, somewhat resembling a helmet, but with one side protuberant: it is formed of hard membrane; the hollow base alone is viscid, and this rests on and is covered by a narrow strip of membrane, which is easily pushed away, and answers to the pouch in Orchis. The whole upper part of the helmet