1843-1862] INSECT FERTILISATION 257 



interested by the abstract (too brief) of your lecture at the Letter 589 

 Royal Institution. Many of the facts alluded to are full of in- 

 terest for me. But on one point I should be infinitely obliged 

 if you could procure me any information : namely, with respect 

 to sweet-peas. I am a great believer in the natural crossing 

 of individuals of the same species. But I have been assured 

 by Mr. Cattell, 1 of Westerham, that the several varieties of 

 sweet-pea can be raised close together for a number of years 

 without intercrossing. But on the other hand he stated that 

 they go over the beds, and pull up any false plant, which 

 they very naturally attribute to wrong seeds getting mixed 

 in the lot. After many failures, I succeeded in artificially 

 crossing two varieties, and the offspring out of the same 

 pod, instead of being intermediate, was very nearly like the 

 two pure parents ; yet in one, there was a trace of the cross, 

 and these crossed peas in the next generation showed still 

 more plainly their mongrel origin. Now, what I want to 

 know is, whether there is much variation in sweet-peas which 

 might be owing to natural crosses. What I should expect 

 would be that they would keep true for many years, but that 

 occasionally, perhaps at long intervals, there would be a 

 considerable amount of crossing of the varieties grown close 

 together. Can you give, or obtain from your father, any 

 information on this head, and allow me to quote your 

 authority ? It would really be a very great favour and 

 kindness. 



To J. D. Hooker. 



Letter 590 



The genera Sc&vola and Leschenaultia^ to which the following letter 

 refers, belong to the Goodeniacese (Goodenovieae, Bentham & Hooker), 

 an order allied to the Lobeliaceae, although the mechanism of fertilisation 

 resembles rather more nearly that of Campanula. The characteristic 

 feature of the flower in this order is the indusium^ or, as Delpino 2 calls 

 it, the " collecting cup " : this cuplike organ is a development of the 

 style, and serves the same function as the hairs on the style of Campanula, 

 namely, that of taking the pollen from the anthers and presenting it to 

 the visiting insect. During this stage the immature stigma is at the 

 bottom of the cup, and though surrounded by pollen is incapable of 

 being pollinated. In most genera of the order the pollen is pushed 

 out of the indusium by the growth of the style or stigma, very much as 



1 The nurseryman he generally dealt with. 



2 Delpino's observations on Dichogamy, summarised by Hildebrand 

 in Bot. Zeitung, 1870, p. 634. 



VOL. II. 17 



