one minute and a half; in an Odontoglossum in two minutes; and in neither of these Orchids was there any free nectar. On the other hand, in Angræcum sesquipedale, which has free nectar stored within the lower end of the nectary, the disc of the pollinium, when removed from the plant and with its surface disturbed, was strongly adhesive after forty-eight hours.
Sarcanthus teritifolius offers a more curious case. The disc quite lost its viscidity and set hard in less than three minutes. Hence it might have been expected that no fluid would have been found in the nectary, but only in the intercellular spaces; nevertheless there was fluid in both places, so that here we have both conditions combined in the same flower. It is probable that insects would sometimes rapidly suck the free nectar and neglect that between the two coats; but even in this case I strongly suspect that they would be delayed by a totally different means in sucking the free nectar, so as to allow the viscid matter to set hard. In this plant, the labellum with its nectary is an extraordinary organ. I wished to have had a drawing made of its structure; but found that it was as hopeless as to give a drawing of the wards of a complicated lock. Even the skilful Bauer, with numerous figures and sections on a large scale, hardly makes the structure intelligible. So complicated is the passage, that I failed in repeated attempts to pass a bristle from the outside of the flower into the nectary; or in a reversed direction from the cut-off end of the nectary to the outside. No doubt an insect with a voluntarily flexible proboscis could pass it through the passages, and thus reach the nectar; but in effecting this, some delay would be caused; and time would be thus allowed for the
