XVI PEEFAOE. 



new heterostyled genera are added to the family; 

 Dr. Koehne does not believe that any species of Lager- 

 Stroemia is, or has been, heterostyled and trimorphic. 

 He has also sent me an outline of an important view, 

 well worth following out, namely, that heterostylism has 

 arisen through the niodiflqation of plants which were 

 teaiding to become polygamous or dioecious. 



It is stated at p. 187 that Mr. Leggett felt some 

 doubt whether Pontederia cordata was trimorphic and 

 heterostyled ; but he has since written to me that his 

 doubts are removed : see also to this effect, in Bull. 

 Torrey Bot. Club, vol. vi.. 1877, p. 170. All three 

 forms of this Pontederia appear to be highly variable. 

 He informs me that humble-bees are the fertilisers. 



With respect to the origin of the dioecious state, 

 which is discussed in the beginning of the seventh 

 chapter, Hermann Miiller has given some interesting, 

 remarks in Kosmos, 1877, p. 290, The same author- 

 shows (Ibid,, p. 130) that Valeriana dioica. exists under 

 four forms closely allied to the four presented by 

 Bhamnus, as described in this same chapter. It is 

 much to be desired that some one should experimentise 

 on these forms and make out their meaning. Bemet 

 has published (Bull. Soc. Bot. Erance, tom. xxv. 

 1878) a paper entitled, 'Disjonction des sexes dans 

 VEuonymus Evropseus, which may be compared with 

 my observations on the same plant. I have stated 

 at p. 298 that I could never find an hermaphrodite 

 plant of the common holly, but according to 

 Mr. Hibberd {Gard. Chron, 1877, pp. 39 and 776) 

 such occur among the many cultivated varieties. 

 The evidence, however, is far from conclusive, for it 

 does not appear that Mr. Hibberd ever observed under 

 the microscope pollen taken from a plant known 

 to produce berries. Trees of Juglans dnerea in the 



