THE ANGIOSPERMAE 



1279 



%'^: 



Fig. 121 5. — Lythrum salicario. Trimorphic flowers. A, In- 

 florescence. B, Long style, long and medium stamens. C, 

 Medium style, long and short stamens. D, Short style, 

 long and medium stamens. (Partly after Darivin.) 



Stamens have pink filaments and bright green pollen. The seeds of the 

 long-styled ovaries are the biggest, the ratio being i : 083 : 070, and the 

 same difference of size is shown by the pollen grains. All three types of 

 plant are about equally common. 



As there are nine different sets of sex organs among the three types and 

 as each set of stamens occurs twice over, there are eighteen possibilities in 

 pollination. Thus the stigma of the long-styled flower may be pollinated in 

 two ways " legitimately ", i.e., from the long stamens of both the other types 

 of flower, and in four ways " illegitimately ", from the short and mid- 

 length stamens. The first two unions are abundantly fertile, the latter four 

 are highly sterile. The same is true of the flowers with mid-length or short 

 styles, although the mid-styled form is more generally fertile. 



We have already spoken of the importance of autogamy, or self-pollina- 

 tion, as a secondary means of securing pollination in case of the failure of 



