18621871] JOHN SCOTT 317 



and Catasetum, for I am completely bewildered : it will rest Letter 640 

 with you to settle these points by your excellent observations 

 and experiments. I must own I never could help doubting 

 Dr. Hooker's case of the poppy. You may like to hear what 

 I have seen this morning : I found l a primrose plant with 

 flowers having three pistils, which when pulled asunder, 

 without any tearing, allowed pollen to be placed on ovules. 

 This I did with three flowers pollen-tubes did not protrude 

 after several days. But this day, the sixteenth (N.B. 

 primulas seem naturally slowly fertilised), I found many 

 tubes protruded, and, what is very odd, they certainly seemed 

 to have penetrated the coats of the ovules, but in no one 

 instance the foramen of the ovule ! ! I mention this because 

 it directly bears on your explanation of Dr. Criiger's case. 2 

 I believe that your explanation is right ; I should never have 

 thought of it ; yet this was stupid of me, for I remember 

 thinking that the almost closed imperfect flowers of Viola 

 and Oxalis were related to the protrusion of the pollen-tubes. 

 My case of the Aceras* with the aborted labellum squeezed 

 against stigma supports your view. Dr. Cruger's notion 

 about the ants was a simple conjecture. About cryptogamic 



1 See Letter 658. 



2 Cruger's case here referred to is doubtless the cleistogamic fertilisa- 

 tion of Epidendrum, etc. Scott discusses the question of self-fertilisation 

 at great length in a letter to Darwin dated April, and obviously written 

 in 1863. In Epidendrum he observed a viscid matter extending from 

 the stigmatic chamber to the anther : pollen-tubes had protruded from the 

 anther not only where it was in contact with the viscid matter, but also 

 from the central part, and these spread " over the anterior surface of the 

 rostellum downward into the stigma." Criiger believed the viscid matter 

 reaching the anther was a necessary condition for the germination of the 

 pollen-grains. Scott points out that the viscid matter is produced in 

 large quantity only after the pollen-grains have penetrated the stigma, 

 and that it is, in fact, a consequence, not a preliminary to fertilisation. 

 He finally explains Cruger's case thus : " The greater humidity and 

 equability of temperature consequent on such conditions [i.e. on the 

 flowers being closed] is, I believe, the probable cause of these abnormally 

 conditioned flowers so frequently fertilising themselves." Scott also calls 

 attention to the danger of being deceived by fungal hyphae in observa- 

 tions on germination of pollen. 



3 See Fertilisation of Orchids., Ed. II., p. 258 : the pollen germinated 

 within the anther of a monstrous flower. 



