108 HETEROSTYLED DIMORPHIC PLANTS. CHAP. III. 



We see in this table that the fertility of the two 

 legitimate unions to that of the two illegitimate 

 together is as 100 to 35, judged by the proportion of 

 flowers which produced fruit ; and as 100 to 32, judged 

 by the average number of seeds per fruit. But the 

 small number of fruit yielded by the 18 long-styled 

 flowers in the first line was probably accidental, and 

 if so, the difference in tne proportion of legitimately 

 and illegitimately fertilised flowers which yield fruit is 

 really greater than that represented by the ratio of 

 100 to 35. The 18 long-styled flowers illegitimately 

 fertilised yielded no seeds, not even a vestige of one. 

 Two long-styled plants which were placed under a net 

 produced 138 flowers, besides those which were arti- 

 ficially fertilised, and none of these set any fruit ; nor 

 did some plants of the same form which were pro- 

 tected during the next summer. Two other long- 

 styled plants were left uncovered (all the short-styled 

 plants having been previously covered up), and 

 humble-bees, which had their foreheads white with 

 pollen, incessantly visited the flowers, so that their 

 stigmas must have received an abundance of pollen, 

 yet these flowers did not produce a single fruit. We 

 may therefore conclude that the long-styled plants 

 are absolutely barren with their own-form pollen, 

 though brought from a distinct plant. In this re- 

 spect they differ greatly from the long-styled English 

 plants of P. offieincdis which were found by me to 

 be moderately self-fertile; but they agree in their 

 behaviour with the German plants of P. officinalia 

 experimented on by Hildebrand. 



Eighteen short-styled flowers legitimately fertilised 

 yielded, as may be seen in Table 20, 15 fruits, each 

 having on an average 2 * 6 seeds. Four of these fruits 

 contained the highest possible number of seeds, namely 



