106 HETEROSTYLED DIMORPHIC PLANTS. CHAP. III. 



times thrice as long as that of the short-styled; but 

 from an average of ten measurements of both, its 

 length to that of the short-styled was as 100 to 56. 

 The stigma varies in being more or less, though 

 slightly, lobed. The anthers also vary much in 

 length in both forms, but in a greater degree in the 

 long-styled than in the short-styled form; many in 

 the former being from 80 to 63, and in the latter 

 from 80 to 70 divisions of the micrometer in length. 

 From an average of seven measurements, the short- 

 styled anthers were to those from the long-styled as 

 100 to 91 in length. Lastly, the pollen-grains from 

 the long-styled flowers varied between 13 and 11.5 

 divisions of the micrometer, and those from the short- 

 styled between 15 and 13. The average diameter of 

 25 grains from the latter, or short-styled form, was 

 to that of 20 grains from the long-styled as 100 to 

 91. We see, therefore, that the pollen-grains from 

 the smaller anthers of the shorter stamens in the long- 

 styled form are, as usual, of smaller size than those 

 in the other form. But what is remarkable, a larger 

 proportion of the grains were small, shrivelled, and 

 worthless. This could be seen by merely comparing 

 the contents of the anthers from several distinct plants 

 of each form. But in one instance my son found, by 

 counting, that out of 193 grains from a long-styled 

 flower, 53 were bad, or 27 per cent.; whilst out of 

 265 grains from a short-styled flower only 18 were 

 bad, or 7 per cent. From the condition of the pollen 

 in the long-styled form, and from the extreme varia- 

 bility of all the organs in both forms, we may perhaps 

 suspect that the plant is undergoing a change, and 

 tending to become dioecious. 



My son collected in the Isle of Wight on two occa- 

 sions 202 plants, of which 125 were long-styled and 



