18651881] F. MULLER 367 



as the upper surface will be somewhat exposed to the dawning Letter 688 

 light, it is perhaps diaheliotropism which explains your extra- 

 ordinary case. 



To F. M tiller. Letter 689 



Down, April I2th, iS8i. 



I have delayed answering your last letter of Feb. 25th, 

 as I was just sending to the printers the MS. of a very little 

 book on the habits of earthworms, of which I will of course 

 send you a copy when published. I have been very much 

 interested by your new facts on paraheliotropism, as I think 

 that they justify my giving a name to this kind of movement, 

 about which 1 long doubted. I have this morning drawn up 

 an account of your observations, which I will send in a few 

 days to Nature} I have thought that you would not object 

 to my giving precedence to paraheliotropism, which has been 

 so little noticed. I will send you a copy of Nature when 

 published. I am glad that I was not in too great a hurry 

 in publishing about Lagerstni'inia?- I have procured some 

 plants of Melastomaceae, but I fear that they will not flower 

 for two years, and I may be in my grave before I can repeat 

 my trials. As far as I can imperfectly judge from my 

 observations, the difference in colour of the anthers in this 

 family depends on one set of anthers being partially aborted. 

 I wrote to Kew to get plants with differently coloured 

 anthers, but I learnt very little, as describers of dried plants 

 do not attend to such points. I have, however, sowed seeds 



1 Nature, 1881, p. 603. Curious facts are given on the movements 

 of Cassia, Phyllanthus sp., Desmodium sp. Cassia takes up a sunlight 

 position unlike its own characteristic night-position, but resembling rather 

 that of Hcematoxylon (see Power of Movement, fig. 153, p. 369). One 

 species of Phyllanthus takes up in sunshine the nyctitropic attitude 

 of another species. And the same sort of relation occurs in the genus 

 Bauhinia. 



2 Lagerstrcemia was doubtfully placed among the heterostyled plants 

 (Forms of Flowers, p. 167). F. Miiller's observations showed that a 

 totally different interpretation of the two sizes of stamen is possible. 

 Namely, that one set serves merely to attract pollen-collecting bees, who 

 in the act of visiting the flowers transfer the pollen of the longer stamens 

 to other flowers. A case of this sort in Heeria, a Melastomad, was 

 described by Mu'ller (Nature, Aug. 4th, 1881, p. 308), and the view was 

 applied to the cases of Lagerstramia and Heteranthera at a later date 

 (Nature 3 1883, p. 364). See Letters 620-30. 



