122 HBTEROSTYLED DIMOEPHIC PLANTS. Chap. III. 



In the long-styled form the stigmas project aboTe the anthers, 

 and the styles are nearly t-wioe as long as those of the short- 

 styled form, in which the stigmas stand beneath the anthers. 

 The stigmas in many, but not in all the short-styled flowers are 

 larger than those in the long-styled. The anthers of the short- 

 styled flowers stand on a level with the stigmas of the other 

 form ; but the stamens are longer by only one-fourth or one-fifth 

 of their own length than those of the long-styled. Consequently 

 the anthers of the latter do not stand on a level with, but rather 

 above the stigmas of the other form. Differently from what 

 occurs in the following closely allied genus, Sethia, the stamens 

 are of nearly equal length in the flowers of the same form. The 

 poUen-grains of the short-styled flowers, measured in their dry 

 state, are a little larger than those from the long-styled flowers 

 in about the ratio of 100 to 93.* 



Sethia acuminata (Eettheoxtlid^). 



Mr. Thwaites pointed out several years ago t that this plant 

 exists under two forms, which he designated as forma, styUsa et 

 staminea ; and the flowers sent to me by him are clearly hetero- 

 styled. 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 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 shaU hereafter see in 

 the case of the short-styled flowers of Lythrwm salioaria, to the 

 manner in which insects can best transport pollen from the 

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

 poUen-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 obtusifolia is 

 heterostyled like 8. acuminata. 



* F. Miiller remarks in his let- numbers ; but the sepals and petals 



ter to me that the flowers, of which often vary from 5 to 7 ; the sta- 



he carefully examined many spe- mens from 10 to 14, and the pistils 



cimena, are curiously variable from 3 to 4. 



in the number of their parts: t ' Enumeratio Plantarum Zey* 



5 sepals and petals, 10 stamens lanisa,' 1864, p. 54. 

 and 3 pistils are the prevailing 



