CHAP. III. CRATOXYLOX FORMOSUM. 123 



SETHIA ACUMINATA (ERYTHROXYLIOE). 



Mr, Thwaites pointed out several years ago * that this 

 plant exists under two forms, which he designated as 

 forma stylosa et staminea; and the flowers sent to me by 

 him are clearly heterostyled. In the long-styled form the 

 pistil is nearly twice as long, and the stamens half as long 

 as the corresponding organs in the short-styled form. The 

 stigmas of the long-styled seem rather smaller than those 

 of the short-styled. All the stamens in the short-styled 

 flowers are of nearly equal length, whereas in the long- 

 styled they differ in length, being alternately a little longer 

 and shorter; and this difference in the stamens of the two 

 forms is probably related, as we shall hereafter see in the 

 case of the short-styled flowers of Lythrum salicaria, to the 

 manner in which insects can best transport pollen from 

 the long-styled flowers to the stigmas of the short-styled. 

 The pollen-grains from the short-styled flowers, though 

 variable in size, are to those of the long-styled, as far as I 

 could make out, as 100 to 83 in their longer diameter. 

 Sethia oltusifolia is heterostyled like 8. acuminata. 



CRATOXYLON FORMOSUM (HYPERICINE^E). 



Mr. Thiselton Dyer remarks that this tree, an inhabit- 

 ant of Malacca and Borneo, appears to be heterostyled. f 

 He sent me dried flowers, and the difference between the 

 two forms is conspicuous. In the long-styled form the 

 pistils are in length to those of the short-styled as 100 to 

 40, with their globular stigmas about twice as thick. These 

 stand just above the numerous anthers and a little beneath 

 the tips of the petals. In the short-styled form the anthers 

 project high above the pistils, the stigmas of which diverge 

 between the three bundles of stamens, and stand only a 

 little above the tips of the sepals. The stamens in this 

 form are to those of the long-styled as 100 to 86 in length ; 

 and therefore they do not differ so much in length as do 

 the pistils. Ten pollen-grains from each form were meas- 

 ured, and those from the short-styled were to those from 

 the long-styled as 100 to 86 in diameter. This plant, there- 



* ' Enumeratio Plantarum Zcy- t 'Journal of Botany,' London, 

 laniae, ' 1864, p. 54. 1872, p. 26. 



