170 HETEROSTYLKD TRIMOEPHIC PLANTS. Chap. IV. 



stamens in the two other forms. In the mid-styled 

 form, the stigmas pass out between the filaments of 

 the longest stamens (as in the short-styled form of 

 Linum) ; and they stand rather nearer to the upper 

 anthers than to the lower ones. In the short-styled 

 form, the stigmas also pass out between the filaments 

 nearly on a level with the tips of the sepals. The 

 anthers in this latter form and in the mid-styled rise 

 to the same height as the corresponding stigmas in the 

 other two forms. 



Oxalis Valdiviana. — This species, an inhabitant of 

 the west coast of South America, bears yellow flowers. 

 Hildebrand states that theistigmas of the three forms 

 do not differ in any marked manner, but that the pistil 

 of the short-styled form alone is destitute of hairs. 

 The diameters of the pollen-grains are as follows : — 



Dlvlitoiu of lilt 



Micrometer. 



From the longest stamens of short-styled 8 to 



" mid-length " " 7 " 8 



" longest stamens of mid-styled 8 



" shortest " " 6 



" mid-length stamens of long-styled .... 7 



" shortest " " 6 



Therefore the extreme diiference in diameter is as 8.5 

 to 6, or as 100 to 71. The results of Hildebrand's ex- 

 periments are given in the following table, drawn up 

 in accordance with my usual plan. He fertilised each 

 form with pollen from the two sets of anthers of the 

 same flower, and likewise from flowers on distinct 

 plants belonging to the same form; but the effects of 

 these two closely allied kinds of fertilisation differ so 

 little that I have not kept them distinct. 



