18621871] JOHN SCOTT 315 



that such recorded cases must be due to unnatural conditions Letter 639 

 of life ; and think I said so in the Origin}- I am not sure that 

 I understand your result, [nor] whether it means what I have 

 above obscurely expressed. If you can prove the above, do 

 publish ; but if you will not publish I earnestly beg you to let 

 me have the facts in detail ; but you ought to publish, for I 

 may not use the facts for years. I have been much interested 

 by what you say on the rostellum exciting pollen to protrude 

 tubes ; but are you sure that the rostellum does excite them ? 

 Would not tubes protrude if placed on parts of column or 

 base of petals, etc., near to the stigma ? Please look at the 

 Cottage Gardener^ (or Journal of 'Horticulture] to be published 

 to-morrow week for letter of mine, in which I venture to 

 quote you, and in which you will see a curious fact about 

 unopened orchid flowers setting seed in West Indies. Dr. 

 Crliger attributes protrusion of tubes to ants carrying stig- 

 matic secretion to pollen 3 ; but this is mere hypothesis. 

 Remember, pollen-tubes protrude within anther in Neottia 

 nidus-avis. I did think it possible or probable that perfect 

 fertilisation might have been effected through rostellum. 

 What a curious case your Gongora must be : could you spare 

 me one of the largest capsules ? I want to estimate the 

 number of seed, and try my hand if I can make them grow. 



where the phenomenon is fully discussed, Scott's observations (Trans. Bot. 

 Soc. Edin., 1863) are given as the earliest, except for one case recorded 

 by Lecoq (Fecondation, 1862). Interesting work was afterwards done 

 by Hildebrand and Fritz Miiller, as illustrated in many of the letters 

 addressed to the latter. 



1 See Origin of Species, Ed. I., p. 251, for Herbert's observations on 

 self-impotence in Hippeastrum. In spite of the uniformness of the 

 results obtained in many successive years, Darwin inferred that the 

 plants must have been in an "unnatural state." 



2 Journal of Horticulture and Cottage Gardener, March 3ist, 1863. 

 A short note describing Criiger's discovery of self-fertilisation in Cattleya, 

 Epidendrum, etc., and referring to the work of " an excellent observer, 

 Mr. J. Scott." Darwin adds that he is convinced that he has underrated 

 the power of tropical orchids occasionally to produce seeds without the 

 aid of insects. 



3 In Criiger's paper (Linn. Soc.Journ., VIII., 1865 ; read March 3rd 

 1864) he speaks of the pollen-masses in situ being acted on by the 

 stigmatic secretion, but no mention is made of the agency of ants. He 

 describes the pollen -tubes descending " from the [pollen] masses still 

 in situ down into the ovarian canal." 



