Chap. IV. LYTHRUM SALICARIA. 151 



two sets of stamens which correspond in length with 

 the pistil of that form, and which are borne by the 

 other two forms. Such unions are of a legitimate 

 nature. The two next lower compartments show the 

 result of the application of pollen from the two sets of 

 stamens not corresponding in length with the pistil, 

 and which are borne by the other two forms. These 

 unions are illegitimate. The two lowest compartments 

 show the result of the application of each form's own 

 two kinds of pollen from the two sets of stamens be- 

 longing to the same form and which do not equal the 

 pistil in length. These unions are likewise illegiti- 

 mate. The term " own-form pollen " here used does 

 not mean pollen from the flower to be fertilised — for 

 this was never used — but from another flower on the 

 same plant, or more commonly from a distinct plant of 

 the same form. The figure (0) means that no capsule 

 was produced, or if a capsule was produced that it con- 

 tained no good seed. In some part of each row of fig- 

 ures in each compartment, a short horizontal line may 

 be seen; the unions above this line were made in 1862, 

 and below it in 1863. It is of importance to observe 

 this, as it shows that the same general result was ob- 

 tained during two successive years ; but more especially 

 because 1863 was a very hot and dry season, and the 

 plants had occasionally to be watered. This did not 

 prevent the full complement of seeds being produced 

 from the more fertile unions; but it rendered the less 

 fertile ones even more sterile than they otherwise would 

 have been. I have seen striking instances of this fact 

 in making illegitimate and legitimate unions with Pri- 

 mula; and it is well known that the conditions of life 

 must be highly favourable to give any chance of suc- 

 cess in producing hybrids between species which are 

 crossed with difficulty. 



12 



