2 INTRODUCTION. 



the individuals of which exist under two or three 

 forms, differing in the length of their pistils and 

 stamens and in other respects. They were called by 

 me dimorphic and trimorphic, but have since been 

 better named by Hildebrand, heterostyled.* As I 

 have many still unpublished observations with respect 

 to these plants, it has seemed to me advisable to re- 

 publish my former papers in a connected and cor- 

 rected form, together with the new matter. It will be 

 shown that these heterostyled plants are adapted for 

 reciprocal fertilisation; so that the two or three forms, 

 though all are hermaphrodites, are related to one an- 

 other almost like the males and females of ordinary 

 unisexual animals. I will also give a full abstract of 

 such observations as have been published since the ap- 

 pearance of my papers; but only those cases will be 

 noticed, with respect to which the evidence seems fairly 

 satisfactory. Some plants have been supposed to be 

 heterostyled merely from their pistils and stamens 

 varying greatly in length, and I have been myself 

 more than once thus deceived. With some species the 

 pistil continues growing for a long time, so that if old 

 and young flowers are compared they might be thought 



of the Proceedings of the Linnean P. elatior, Jacq. ; and on the 



Society,' vol. vi. 1862, p. 77. Hybrid Nature of the Common 



"On the Existence of Two Oxlip. With Supplementary Re- 



Forms, and on their Reciprocal marks on Naturally Produced Hy- 



Sexual Relation, in Several Species hrids in the Genus Verbascum." 



of the Genus Linum." Ibid. vol. Ibid. vol. x. 1868, p. 437. 

 vii 1863, p. 6fl. * The term " heterostyled " does 



On the Sexual Relations of not express all the differences be- 



the Three Forms of Lythrum sali- tween the forms ; but this is a 



caria." Ibid. vol. iii. 1864. p. 169. failure common in many cases. 



On the Character and Hybrid- As the term has been adopted by 



like Nature of the Offspring from writers in various countries, I am 



the Illegitimate Unions of Dimor- unwilling to change it for that of 



phic and Tnmorphic Plants." lieterogone or heteroqonous, though 



" A V *' 1 C 868 ' & 393 ' this has been P r P sed b y so high 



s bpecinc Differences an authority as Prof. Asa Gray 



between Primula verts, Brit. Fl. see the 'American Naturalist,' 



( var. offinnalM, Linn.), P. vnlgari*, Jan. 1877, p. 42. 

 Brit. Fl. (var. acaulis, Linn.), and 



