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. IV. as I have described under Listera ovata. The flowers are frequented by minute Diptera and Hymenoptera.

Neottia nidus-avis.—I made numerous observations on this plant, the Bird's-nest Orchis, but they are not worth giving, as the action and structure of every part is almost identically the same as in Listera ovata and cordata. On the crest of the rostellum there are about six minute rough points, which seem particularly sensitive to a touch, causing the expulsion of the viscid matter. The exposure of the rostellum to the vapour of sulphuric ether for twenty minutes did not prevent this action, when it was touched. The labellum secretes plenty of nectar, which I mention merely as a caution, because during one cold and wet season I looked several times and could not see a drop, and was perplexed at the apparent absence of any attraction for insects; nevertheless, had I looked more perseveringly, perhaps I should have found some.

The flowers must be freely visited by insects, for all in one large spike had their pollinia removed. Another unusually fine spike, sent me by Mr. Oxenden from South Kent, had borne forty-one flowers, and it produced twenty-seven large seed-capsules, besides some smaller ones. Dr. H. Müller of Lippstadt informs me that he has seen Diptera sucking the nectar and removing the pollinia.

The pollen-masses resemble those of Listera, in consisting of compound grains tied together by a few weak threads; they differ in being much more incoherent; after a few days they swell and overhang the sides and summit of the rostellum; so that if the rostellum of a rather old flower be touched and an explo-