114 HBTEBOSTYLED DIMORPHIC PLANTS. Chap. Ill 



Other species shows that P. Ustorta is so strongly pro- 

 terandrous (the anthers generally falling off before the 

 stigmas are mature) that the flowers must be cross- 

 fertilised by the many insects which visit them. Other 

 species bear much less conspicuous flowers which se- 

 crete little or no nectar, and consequently are rarely 

 visited by insects ; these are adapted for self-fertilisa- 

 tion, though still capable of cross-fertilisation. Ac- 

 cording to Delpino, the Polygonaceae are generally 

 fertilised by the wind, instead of by insects as in the 

 present genus. 



Leuoosmia Btjenettiana (Thtmell«:). 



As Prof. Asa Gray has expressed his belief * that this species 

 and L. acuminata, as well as some species in the allied genus 

 Drymispermnm, are dimorphic or heterostyled, I procured 

 from Kew, through the kindness of Dr. Hooker, two dried 

 flowers of the former species, an inhabitant of the Friendly 

 Islands in the Pacific. The pistil of the long-styled form is to 

 that of the short-styled as 100 to 86 in length; the stigma 

 projects just above the throat of the coroUa, and is surrounded 

 by five anthers, the tips of which reach up almost to its base; 

 and lower down, within the tubular corolla, five other and 

 rather smaller anthers are seated. In the short-styled form, 

 the stigma stands some way down the tube of the corolla, nearly 

 on a level with the lower anthers of the other form : it differs 

 remarkably from the stigma of the long-styled form, in being 

 more papillose, and in being longer in the ratio of 100 to 60. 

 The anthers of the upper stamens in the short-styled form are 

 supported on free filaments, and project above the throat of the 

 corolla, whilst the anthers of the lower stamens are seated in 

 the throat on a level with the upper stamens of the other form. 

 The diameters of a considerable number of grains from both sets 

 of anthers in both forms were measured, but they did not differ 

 in any trustworthy degree. The mean diameter of twenty-two 



•'American Journal of Soi- 'Journal of Botany,' vol. iii. 1865, 

 enoo,' 1865, p. 101, and Seemann's p. 305. 



