262 BOTANY [Chap. X 



Letter 593 all the pollen has been pushed out of the indusium. But my 

 observations are here at fault, for I did not observe the pene- 

 tration of the pollen-tubes. The case is almost parallel with 

 that of Lobelia. Now, I hope you will get two plants of 

 Sccevola, and protect one from insects, leaving the other 

 uncovered, and observe the results, both in the number of 

 capsules produced, and in the average number of seeds in 

 each. It would be well to fertilise half a dozen flowers under 

 the net, to prove that the cover is not injurious to fertility. 



With respect to your case of Aristolochia, I think further 

 observation would convince you that it is not fertilised only 

 by larvae, for in a nearly parallel case of an Arum and an 

 Aristolochia, I found that insects flew from flower to flower. 

 I would suggest to you to observe any cases of flowers which 

 catch insects by their probosces, as occurs with some of the 

 Apocyneae x ; I have never been able to conceive for what 

 purpose (if any) this is effected ; at the same time, if I tempt 

 you to neglect your zoological work for these miscellaneous 

 observations I shall be guilty of a great crime. 



To return for a moment to the indusium : how curious it 

 is that the pollen should be thus collected in a special recep- 

 tacle, afterwards to be swept out by insects' agency ! 



I am surprised at what you tell me about the fewness of 

 the flowers of your native orchids which produce seed-capsules. 

 What a contrast with our temperate European species, with 

 the exception of some species of Ophrys ! — I now know of 

 three or four cases of self-fertilising orchids, but all these are 

 provided with means for an occasional cross. 



I am sorry to say Dr. Criiger is dead from a fever. 



I received yesterday your paper in the Botanische Zeitung 

 on the wood of climbing plants. 2 I have read as yet only 

 your very interesting and curious remarks on the subject as 

 bearing on the change of species ; you have pleased me by 

 the very high compliments which you pay to my paper. I 

 have been at work since March 1st on a new English edition 3 

 of my Origin, of which when published I will send you a 



1 Probably Asclepiadeas. See H. Muller, Fertilisation of Flowers, 

 p. 396. 



2 Fritz Muller, " Ueber das Holz einiger urn Desterro wachsenden 

 Kletterpflanzen." Botanische Zeitung, 1866, pp. 57, 65. 



3 The 4th Edit. 



