Plate 195.— PTEKOSTYLIS BANKSII. 



Family ORCHIDACEzE.J (Genus PTEROSTYLIS, R. Br. 



Pterostylis Banksii fl^ Dr. ex A. Cnnn. in Bot. Mag. t. 3172; Hook. /. Fl. Nov. Zel. i, 248 • 

 Cfieesem. Man. N.Z. Fl. 679. ' 



Pterostylis Banksii, which i.s by far the finest species of the genus found 

 n New Zealand was first discovered by Banks and Solander at Mercury Bay 



F^oran/N^'' Z^f' ^,""T ^""f' ^''} ""^^S"^- S^^^"^^^' ^^ ^is manuscript 

 llZ ! , , Zealand, referred it to the genus Arethvsa, but gave no detailed 

 account of It, for he supposed that it was identical with an Australian plant 

 described m another part of his manuscripts. It was not again seen unti 

 1826 when the talented and enthusiastic Allan Cunningham Vhered 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 

 Worth Cape to Stewart Island, and from sea-level to nearly 4 000 ft 



F. 5a/i/.v.^^ IS usually found along the sides of lightlv 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 tor 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 ar"e found 

 m 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. ''"gcis 



• ^ The remarkable fertilization of Pterostylis was first described by myself 

 in the Transactions of the New Zealand Institute" (vol v p 'i5^ et sea) 

 Ihe 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 extremelv sensitive, hangs out 



Wets ' wr%'' i^^ ^'''' -'^^"^ ^"'■"^^"°- ' ^'^"^^"ient landing-place fo 

 nsects. When touched by an insect it springs up, carrving the Tnsect with 

 t, and thus enclosing it withm the flower. The position then occupied by 

 the lip IS that shown m fig. 2 of the accompanying plate, and the insect is 

 enclosed m the space between the lip and the column. The hood Hke 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 onlv mode of escape is bv crawling up the 

 front of the column and passing between the wings (see fig 4) In doing 

 this It IS f^rst smeared with viscid matter from the rostellum, which proiects 

 at^ the back of the passage between tlie wings, and then drags away the 

 pollinia, which can hardly fail to adhere to its sticky bodv. When visiting 

 another flower it must pass over the stigma before escaping, and can hardlv 

 fail to leave some of the pollinia on its viscid surface. From the above it is 

 clear that the fertilization of the flower depends entirelv on the irritab itv 



ifn itnri'? 1^'fl^ *' ^^'Ji ^^ '^"^^^"'^ '^''^ "" ^"^ ^^^^^^«" I removed the 

 hp from twelve flowers while vonng, so that insect visitors would not be com- 

 pelled to crawl out of the flower bv the passage between the w^K^s of X 

 column. When these flowers commenced to wither thev were examined when 

 It was found that they were not fertilized, and that not a single pollen-mass 



