Chap. III. PTEROSTYLIS LONGIFOLIA. 91 



in the proper manner.* I will mention only two pecu- 

 liarities in the structure of the flowers : the anterior 

 part of the pollen-masses is semi-waxy and the posterior 

 part somewhat friable ; the grains are not cemented 

 together into compound grains, and the single grains 

 are not united by fine elastic threads but by viscid 

 matter; this matter would aid in causing the pollen 

 to adhere to an insect, but I should have thought that 

 such aid was superfluous, as the viscid rostellum is 

 well developed. The other peculiarity is that the 

 labellum, in front of the stigma, and some way beneath 

 it, is furnished with a stiff hinged brush, formed of a 

 series of combs one over the other, which point down- 

 wards. This structure would allow an insect to crawl 

 easily into a flower, but would compel it whilst re- 

 treating to press close against the column ; and in 

 doing so it would remove the pollen-masses, leaving 

 them on the stigma of the next flower which was 

 visited. 



The genus Sobralia is allied to Vanilla, and Mr. 

 Cavendish Browne informs me that he saw a large 

 humble-bee enter a flower of S. macrantha in his 

 hothouse, and when it crawled out it had the two 

 large pollen- masses firmly fixed to its back, nearer to 

 the tail than to the head. The bee then looked about, 

 and seeing no other flower re-entered the same one of 



* For Bmibon see 'Bui. Soc. in the Blue Mountains of New 

 Bot. de France,' torn. i. 18f»4. p. South Wiiles; removed from 

 290. For Tahiti see H. A. Tilley, theiiee to Sydney, a number of 

 'Japan, the Amour, &o./ 1861, p. plants, though {iowerinj? well, have 

 375. For the East Indies tee not borne any seed if left to them- 

 Morren in 'Annals and Mag. of selves, though invariably fertile 

 Nat. Hist.' 1839, vol. iii. p. 6. I when the pollen-masses were re- 

 may give an analogous but more moved and placed on the stigma." 

 striking case from Mr Fitzgerald, Yet the Blue Mountains are less 

 who says "that Sarcochilus par- than one hundred miles dibtaiit 

 vijlorus (one of the Vandeae) pro- fiom Sydney, 

 duces capsules not unfrequently 



