434 ANGIOSPERMAE—DICOTYLEDONES 



axils, each with a single stamen 4-5 mm. long, the yellow anther of which is 

 borne upon a stiff filament and projects from the rosette to this distance, afterwards 

 dehiscing. The pale-yellow tuberculated pollen-grains are very irregular in shape 

 (prismatic, tetrahedral, or bluntly pyramidal), vefy easily scattered, and transferred 

 by the wind to adjoining younger leaf-rosettes bearing female flowers. In rarer 

 cases I noticed a male flower in one leaf-axil and a female flower in that immediately 

 opposite. Self-pollination was then easily possible, for pollen could fall directly 

 on the two branches of the style. Besides the anemophilous flowers now described 

 I also found, on lateral shoots of varying length, female flowers devoid of perianth 

 leaves, relatively small ovaries and very long styles. These were apparently 

 pollinated under water, though I did not observe submerged male flowers. The 

 species may therefore be described as anemo-hydrophilous, and autogamous under 

 certain conditions. 



1028. C. hamulata Kuetz. (Ludwig, op. cit. ; Hegelmaier, op. cit.) — This 

 species also bears submerged flowers, which are sterile according to Hegelmaier. 



I02g. C. autumnalis L. (Ludwig, op. cit; Hegelmaier, op. cit., p. 61 ; 

 Jonsson, Univ. Arsskr., Lund, xx, 1883-4.) — This species belongs to the sub-genus 

 Pseudocallitriche, in which the pollen-grains possess no external coat (extine), an 

 indication of hydrophily. Jonsson describes them as oil-containing and lighter than 

 water, so that they can drift to the stigmas of the female flowers and effect 

 pollination. 



XL. ORDER MELASTOMACEAE R.Br. 

 291. Heeria Schlecht. 



Hermann MuUer states (Nature, London, xxiv, 1881, pp. 307-8) that in the 

 species of this genus there are two kinds of stamen differing in function : the one 

 kind serving to attract insects, while the other produces pollen. {Cf. Vol. I, p. 108.) 



292. Centradenia G. Don (1030. C. floribunda Planch.), 293. Rhexia 

 L. (1031. R. glandtilosa Bertol.), and 294. Monochaetum Naud. 

 (1032. M. ensiferum Naud.) — 



Darwin describes the above three species as self-sterile. 



295. Pleroma D. Don ( = Tibouchina Aubl). 



1033. P. Sellowiana Cogn. (Ludwig, Biol. Centralbl., Erlangen, vi, 1886-7.) — 

 Ludwig says that the flowers of this species are at first pure white, afterwards assum- 

 ing a purple-red colour. {Cf. Vol. I, p. 86.) 



Darwin describes species of Pleroma as self-sterile. 



XLL ORDER LYTHRARIEAE JUSS. 



(including Granateae Don.) 



This order includes a large number of trimorphous and dimorphous species. 

 Among the former are Lythrum Salicaria Z., L. Graefferi Tenore, and species of 

 the genera Nesaea and Lagerstroemia. Among dimorphous forms are Lythrum 



