50 INTRODUCTION 
(Hildebrand). Among Monocotyledones, Pontederia alone is known to be trimorphous 
(Fr. Miiller); Kerner, however, gives also Colchicum autumnale. 
Connarus falcatus &/. forms the transition between trimorphous and dimorphous 
plants. According to Burck (Ann. Jard. bot., Buitenzorg, vi, 1887, p. 251) the 
flowers of this species are trimorphous in structure, but the anthers of the inner whorl 
always remain closed. This same phenomenon occurs in Averrhoa Carambola Z. 
Polygonum amphibium (Knuth, ‘Bl. u. Insekt. a, d. nordf. Ins.,’ p. 125), is perhaps 
also imperfectly trimorphous. 
Dimorphous species are particularly abundant in the genus Oxalis, 51 being 
enumerated by Hildebrand; also in Linum (30 species according to Alefeld), 
and Primula (36 species). Other dimorphous Primulaceae are Hottonia palustris 
(Sprengel), species of Pulmonaria (Darwin), Gregoria Vitaliana (Scott), and species 
of Dionysia(Kuhn). Other dimorphous Linaceae belong to the genera Erythroxylon, 
Reinwardtia and Hugonia (Kuhn), 
The family of the Rubiaceae is also rich in dimorphous plants: e.g. species 
of Asperula (Kuhn), Knoxia (do.), Chasalia (do.), Mitchella (Darwin, Kuhn), 
Hedynotis (Fr. Miiller, Kuhn), Ophiorrhiza (Kuhn), Cinchona (do.), Nertera (do.), 
Luculia (Kuhn), Pentas (Hirn), Otomeria (do.), Dirichletia and Pentanisia (do.), 
Bouvardia leiantha (Bailey), Borreria (Fr. Miiller), Manettia (do.), Faramea (do.), 
Androsacme longifolia (Clarke), Randia uliginosa (do.), species of Houstonia 
(Meehan); Psychotria aurantiaca, perforata, sarmentosa var. angustata, montana, 
robusta, and expansa (Burck), Chasalia lurida (do.), Cephaélis Beerii and Ipecacuanha 
(do.), species of Saprosma (do.), Serissa foetida (do.), Knoxia lineata (do.), species 
of Hedyotis (do.), Spermacoce verticillata (do.), Cinchona succirubra, Calisaya, 
Ledgeriana, officinalis, and carabayensis (do.), C. micrantha (Darwin). 
The family of the Turneraceae also contains numerous dimorphous species. 
J. Urban (Jahrb. bot. Garts, Berlin, ii, 1883) enumerates 48 completely and 6 
incompletely dimorphous species. Many of the Lythraceae are dimorphous; e.g. 
(according to K6éhne, ‘Monogr. d. Lythraceen’) species of the genus Lythrum 
belonging to the group Pythagorea (except L. maritimum, which is homostylous), 
species of Pemphis, Adenaria, Rotala floribunda, 
Among Boraginaceae the following are dimorphous: Pulmonaria officinalis 
(Darwin, Hildebrand), P. angustifolia Z. = P. azurea Bess. (Darwin), Cordia 
(Darwin), Amsinckia (Kuhn), Arnebia (Kuhn), Lithospermum canescens (Bessey), 
Macrotomia perennis (Clarke); among Gentianaceae the following, Menyanthes 
trifoliata (Kuhn), Villarsia Humboldtianum (Fr. Miiller), species of Hockinia and 
Limnanthemum (Kuhn). Darwin, however, does not regard Amsinckia and Arnebia 
as dimorphous, but only as possessing stamens and styles of variable length. 
Dimorphous Hypericaceae :—Cratoxylon formosum (Darwin, Dyer); Stercu- 
liaceae :—Melochia parvifolia A. &. K. in Caracas (Ernst); Silenaceae :—Silene 
petraea (Lalanne, Caille); Rhamnaceae:—Rhamnus lanceolatas Pursh (Darwin); 
Plumbaginaceae :—Brazilian species of Plumbago and Statice (Fr. Miiller), Statice 
Limonium in Belgium (MacLeod); Verbenaceae:—species of Aegiphila (Darwin); 
Santalaceae:—Thesium intermedium (Schulz); Amarantaceae:—Chamissoa, with 
transition to dicliny (Fr. Miller). 
The following species are incompletely heterostylous:—Narcissus Tazetta var. 
