8-4 iLEETHUSE^. Chap. III. 



the summit of one pillar in this latter flower, all the 

 other pillars still stood upright and unbroken. I looked 

 at the flowers of some surrounding plants, and every- 

 where found, as I had so often done before, broken-down 

 pillars and masses of pollen on the stigmas. 



From the usual state of the pillars of pollen, as 

 well as from the gnawed condition of the ridges on the 

 labellum, it may be safely inferred that insects of some 

 kind visit the flowers, disturb the pollen, and leave 

 masses of it on the stigmas. We thus see that the 

 turning down of the distal portion of the labellum, by 

 which a temporary landing-place and an open door are 

 afforded,— the upturned labellum, by which the flower 

 is made tubular so that insects are compelled to crawl 

 close by the stigmatic surface, — the pollen readily 

 cohering to any object, and standing in friable pillars 

 protected from the wind, — and, lastly, the large masses 

 of pollen above and below that layer of grains, the 

 tubes of which alone penetrate the edge of the stigma, — 

 are all co-ordinated structures, far from useless ; and 

 they would be quite useless if these flowers were always 

 self- fertilised. 



To ascertain how far the early penetration of the 

 upper edge of the stigma by the tubes of those grains 

 which rest on it, is effectual for fertilisation, I covered 

 up a plant, just before the flowers opened, and removed 

 the thin net as soon as they had begun to wither. From 

 long experience I am sure that this temporary cover- 

 ing could not have injured their fertility. The four 

 covered flowers produced seed-capsules as fine in ap- 

 pearance as those on any of the surrounding plants. 

 When ripe, I gathered them, and likewise capsules 

 from several of the surrounding plants, growing under 

 similar conditions, and weighed the seed in a chemical 

 balance. The seeds from the four capsules on the 



