Pterostylis Banksii, which is by far the finest species of the genus found in New Zealand, was first discovered by Banks and Solander at Mercury Bay in November, 1769, during Cook's first voyage. Solander, in his manuscript Flora of New Zealand, referred it to the genus Arethusa, but gave no detailed account of it, for he supposed that it was identical with an Australian plant described in another part of his manuscripts.

It was not again seen until 1826, when the talented and enthusiastic Allan Cunningham gathered it on the banks of the Kawakawa River, Bay of Islands. Since then it has been found to range through almost the whole length of the Dominion, from the North Cape to Stewart Island, and from sea-level to nearly 4,000 ft.

P. Banksii is usually found along the sides of lightly wooded gullies, or on the margin of forest lands, and sometimes occurs in considerable quantities. It is variable in size, sometimes attaining a height of quite 18 in. or even more, at other times barely reaching 6 in.

Specimens of the sizes quoted above have been collected by myself in a single locality growing under uniform conditions; but, speaking generally, the taller specimens are found in sheltered places along the sides of ravines, and the smaller in more open situations.

The large green flowers, often streaked with red or reddish-brown, and with the three sepals all furnished with long filiform tails, have a most curious and bizarre appearance, and always attract the notice of strangers when seen for the first time.

The remarkable fertilization of Pterostylis was first described by myself in the "Transactions of the New Zealand Institute" (vol. v, p. 352 et seq.). The upper sepal and petals are connate into a hood, at the back of which the column is placed. The tip of the lip, which is extremely sensitive, hangs out of the entrance to the flower, thus forming a convenient landing-place for insects. When touched by an insect it springs up, carrying the insect with it, and thus enclosing it within the flower.

The position then occupied by the lip is that shown in fig. 2 of the accompanying plate, and the insect is enclosed in the space between the lip and the column. The hood-like flower prevents any escape to the right or left of the lip, and as the lip remains closely appressed to the projecting wings of the upper part of the column as long as the insect is present, the only mode of escape is by crawling up the front of the column and passing between the wings (see fig. 4).

In doing this, it is first smeared with viscid matter from the rostellum, which projects at the back of the passage between the wings, and then drags away the pollinia, which can hardly fail to adhere to its sticky body.

When visiting another flower it must pass over the stigma before escaping, and can hardly fail to leave some of the pollinia on its viscid surface. From the above, it is clear that the fertilization of the flower depends entirely on the irritability of the lip.

With the view of proving this, on one occasion I removed the lip from twelve flowers while young, so that insect visitors would not be compelled to crawl out of the flower by the passage between the wings of the column. When these flowers commenced to wither they were examined, when it was found that they were not fertilized, and that not a single pollen-mass had been removed from the anther.

I have also repeatedly placed minute insects on the lip, thus causing them to become entrapped, and in several instances I have seen these escape from the flower in the manner described above, bearing pollinia on their backs.

The whole of the New Zealand species of Pterostylis are fertilized in the manner described above; and according to the researches of the late Mr. Fitzgerald, it is also the manner employed in the Australian species.