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 have many still unpublished observations with respect 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 i. 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 

 another 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 

 appearance 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 myseK 

 more than once thus deceived. With some species the 



of the Proceedings of the Linoean 

 Society," vol. \i. 1862, p. 77. 



" On the Existence of Two 

 Forms, and on their Eeoiprocal 

 Sexual Relation, in several Species 

 of the Genus Linum." Ibid. vol. 

 vii. 1863, p. 69. 



" On the Sexual Relations of the 

 Three Forms of Lythrum salicaria.' 

 Ibid. vol. viii. 1804, p. 169. 



" On the Character and Hybrid- 

 like Nature of the Offspring from 

 tho Illegitimate Unions of Dimor- 

 phic and Trimorphic Plants." 

 Ibid. vol. X. 1868, p. 393. 



" On the Specific Differences 

 between Primula veris, Brit. Fl. 

 (var. officinalis, Linn.), P. vulgaris, 

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



P. elatior, Jacq. ; and on tho 

 Hybrid Nature of the Common 

 Oxlip. "With Supplementary Re- 

 marks on Naturally Produced Hy- 

 brids ill the Genus Verbascum." 

 Ibid. vol. X. 1868, p. 437. 



* The term " heterostyled " does 

 not express all the differences be- 

 tween the forms; but this is a 

 failure common in many cases. 

 As the term has been adopted by 

 writers in various countries, I am 

 unwilling to change it fur that ot 

 hetej-ogone or lieterogonous, though 

 this has been proposed by so high 

 an authority as Prof Asa Gray : 

 see the 'American Naturalist 

 Jan. 1877, p. 42. 



