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280 England as those of O. muscifera, which cannot fertilise itself and is imperfectly fertilised by insects, so that a large proportion of the flowers drop off unimpregnated. Ophrys aranifera is found in large numbers in Liguria, yet Delpino estimates that not more than one out of 3000 flowers produces a capsule. Mr. Cheeseman says that with the New Zealand Pterostylis trullifolia much less than a quarter of the flowers, which are beautifully adapted for cross-fertilisation, yield capsules; whereas with the allied Acianthus sinclairii, the flowers of which equally require insect-aid for their fertilisation, seventy-one capsules were produced by eighty-seven flowers; so that this plant must produce an extraordinary number of seeds; nevertheless in many districts it is not at all more abundant than the Pterostylis. Mr. Fitzgerald, who in Australia has particularly attended to this subject, remarks that every flower of Thelymitra carnea fertilises itself and produces a capsule; yet it is not nearly so common as Acianthus fornicatus, "the majority of the flowers of which are unproductive. Phajus grandifolius and Calanthe veratrifolia grow in similar situations. Every flower of the Phajus produces seeds, only occasionally one of the Calanthe, yet Phajus is rare and Calanthe common."

The frequency with which throughout the world members of various Orchideous tribes fail to have their flowers fertilised, though these are excellently constructed for cross-fertilisation, is a remarkable fact. Fritz Müller informs me that this holds good in the luxuriant forests of South Brazil with most of the Epidendreæ, and with the genus Vanilla. For instance,