is,; r862] FLORAL SYMM ETRY 



iKinu :1) , a flow< r bilalerall) diffi rent : one other, I obs< rve, has i iter 581 

 half its calyx purple. Is this not very curious, and oppo 

 to the morphological idea that a flower is a d con- 



tinuous spire of leaves ? Docs it not look as if flowers were 

 normally bilateral ; just in the same way as we now know 

 that the radiating star-fish, etc., are bilateral? The case 

 rem iii' Is me of those inse< ts with exactly half having sea mdary 

 male characters and the other half female. 



It is interesting to note his 1 hange of view in later years. In an undated 

 letter written to Mr. Spencer, probably in 1873, he says : "Withres] 

 to .1 ymmetry in the flowers themselves, I remain contented, from all that 

 I have seen, with adaptation to visits of insects. There is, however, 

 another factor which it is likel] '" may have come into play— viz., 



the protection of the anthers and pollen from the injurious effects ol 

 rain. I think so becau e several flowers inhabiting rainy countries, as 

 A. Kemer has lately shown, bend their heads down in rainy weather." 



To J. D. 1 [ooker. 1 :tc( 5 s> 



June [1855]. 



This is an early example of Darwin's interest in the movements of 

 plants. Sleeping plants, as is well known, may acquire a rhythmic 

 movement differing from their natural period, but the pre* 1 experiment 

 here described has not, as far as known, been carried out. See Pfeffi 

 Periodische Bewegungen t [875, p. 32. 



I thank you much for Hedysarum : I do hope it is not very 

 precious, for, as I told you, it is for probably a most foolish 

 purpose. 1 read somewhere that no plant closes its leaves 

 so promptly in darkness, and I want to cover it up daily for 

 hall an hour, and see if I can teach it to close by itself, or 

 more easily than at first in darkness. 1 am rather puzzled 

 about its transmission, from not knowing how tender it is. . . . 



To J. D. 1 looker. Lettei 



Down, July 19th, [856. 

 I thank you warmly for the very kind manner with which 

 you have taken 1113- teeniest. It will, in truth, be a most 

 important service to me ; for it is absolutely necessary that 1 

 should discuss single and double creations as a very crucial 

 point on the general origin of species, and I must confess. 

 with the aid of all sorts o\ visionary hypotheses, a very hostile 

 one. I am delighted that you will take up possibility of 

 crossing ; no botanist has done so, which I have long 



