Chap. III. PTEROSTYLIS LONGIFOLIA. 89 



flowers in a withered condition, and seventy-one of these 

 had pollen on their stigmas, and only twenty-eight had 

 all four poUinia still within their anthers. All the 

 New Zealand species bear solitary flowers, so that dis- 

 tinct plants cannot fail to be intercrossed. I may add 

 that Mr. Fitzgerald also placed a small beetle on (he 

 labellum of P. longifolia, which was instantly carried 

 into the flower and imprisoned; afterwards he saw 

 it crawl out with two poUinia attached to its back. 

 Nevertheless he doubts, from reasons which seem to 

 me quite insufiicient, whether the sensitiveness of the 

 labellum is not as great a disadvantage as an advan- 

 tage to the plant. 



Mr. Fitzgerald has described another Orchid belong- 

 ing to the same sub-tribe, Caladenia dimorplia, which 

 has an irritable labellum. He kept a plant in his room, 

 and says : " A house-fly lighting on the lip was carried 

 by its spring against the column, and becoming en- 

 tangled in the gluten of the stigma, and struggling to 

 escape, removed the pollen from the anther and smeared 

 it on the stigma." He adds, " Without some such aid 

 the species of this genus never produce seed." But 

 from the analogy of other Orchids we may feel sure 

 that insects usually behave very differently from the 

 fly which he saw caught on the stigma, and no doiibt 

 they carry the pollen-masses from plant to plant. The 

 labellum of another Australian genus, Calsena, one oi 

 the Arethuseae, is said by Dr. Hooker * to be irritable ; 

 so that when touched by an insect it shuts up suddenly 

 against the column, and temporarily encloses its prey 

 as it were within a box. The labellum is covered by 

 curious papillae, which, as far as Mr. Fitzgerald has 

 seen, are not gnawed by insects. 



' Flora of Tasmania,' vol. ii. p. 17. 



