18431862] INSECT FERTILISATION 26l 



To J. D. Hooker. Letter 592 



Nov. 3rd [1862]. 



Do you remember the scarlet Leschenaultia formosa with 

 the sticky margin outside the indusium ? Well, this is the 

 stigma at least, I find the pollen-tubes here penetrate and 

 nowhere else. What a joke it would be if the stigma is always 

 exterior, and this by far the greatest difficulty in my crossing 

 notions should turn out a case eminently requiring insect aid, 

 and consequently almost inevitably insuring crossing. By the 

 way, have you any other Goodeniaceae which you could lend 

 me, besides Leschenaultia and Scczvola, of which I have seen 

 enough ? 



I had a long letter the other day from Crocker of 

 Chichester ; he has the real spirit of an experimentalist, 

 but has not done much this summer. 



To F. Miiller. Letter 593 



Down, April 9th and I5th [1866]. 



I am very much obliged by your letter of February I3th, 

 abounding with so many highly interesting facts. Your 

 account of the Rubiaceous plant is one of the most extraordi- 

 nary that I have ever read, and I am glad you are going to 

 publish it. I have long wished some one to observe the 

 fertilisation of Sccevola, and you must permit me to tell you 

 what I have observed. First, for the allied genus of Leschen- 

 aultia : utterly disbelieving that it fertilises itself, I introduced 

 a camel-hair brush into the flower in the same way as a bee 

 would enter, and I found that the flowers were thus fertilised, 

 which never otherwise happens ; I then searched for the 

 stigma, and found it outside the indusium with the pollen- 

 tubes penetrating it ; and I convinced Dr. Hooker that 

 botanists were quite wrong in supposing that the stigma lay 

 inside the indusium. In Sc&vola microcarpa the structure 

 is very different, for the immature stigma lies at the base 

 within the indusium, and as the stigma grows it pushes the 

 pollen out of the indusium, and it then clings to the hairs 

 which fringe the tips of the indusium ; and when an insect 

 enters the flower, the pollen (as I have seen) is swept from 

 these long hairs on to the insect's back. The stigma continues 

 to grow, but is not apparently ready for impregnation until it 

 is developed into two long protruding horns, at which period 



