Chap. IV. LYTHRUM SALICARIA. 137 



CHAPTER IV. 



Heteeostyled Teimoephic Plants. 



Lythrum salicaria— Description of the three forms— Their power and 

 complex manner of fertilising one another— Eighteen different 

 unions possible — Mid-styled form eminently feminine in nature — 

 Lythrum Grsefferi likewise trimorphic — L. thymifolia dimorphic — 

 L. hyssopifolia homostyled — Nesaea verticillata trimorphic — Lager- 

 strcemia, nature doubtful — Oxalis, trimorphic species of— O. Valdi- 

 viana — O. Eegnelli, the illegitimate unions quite barren — O. spe- 

 ciosa — O. sensitiva — Homostyled species of Oxalis — Pontederia, 

 the one monocotyledonous genus known to include heterostyled 

 species. 



In the previous chapters various heterostyled dimor- 

 phic plants have been described, and now we come to 

 heterostyled trimorphic plants, or those which present 

 three forms. These have been observed in three 

 families, and consist of species of Lythrum and of the 

 allied genus Nessea, of Oxalis and Pontederia. In 

 their manner of fertilisation these plants offer a more 



remarkable case than can be found in any other plant 

 or animal. 



Lythrum salicaria. — The pistil in each form differs 

 from that in either of the other forms, and in each 

 there are two sets of stamens different in appearance 

 and function. But one set of stamens in each form 

 corresponds with a set in one of the other two forms. 

 Altogether this one species includes three females or 

 female organs and three sets of male organs, all as 

 distinct from one another as if they belonged to dif- 

 ferent species; and if smaller functional differences 



