CHAP. IV. LYTHRUM SALICARIA. 15 



From this summary and the several foregoing tables 

 we see that it is only pollen from the longest stamens 

 which can fully fertilise the longest pistil; only that 

 from the mid-length stamens, the mid- length pistil; 

 and only that from the shortest stamens, the shortest 

 pistil. And now we can comprehend the meaning of 

 the almost exact correspondence in length between 

 the pistil in each form and a set of six stamens 

 in two of the other forms; for the stigma of each 

 form is thus rubbed against that part of the insect's 

 body which becomes charged with the proper pollen. 

 It is also evident that the stigma of each form, 

 fertilised in three different ways with pollen from 

 the longest, mid-length, and shortest stamens, is acted 

 on very differently, and conversely, that the pollen from 

 the twelve longest, twelve mid-length, and twelve 

 shortest stamens acts very differently on each of the 

 three stigmas; so that there are three sets of female 

 and of male organs. Moreover in most cases the six 

 stamens of each set differ somewhat in their fertilising 

 power from the six corresponding ones in one of the 

 other forms. We may further draw the remarkable 

 conclusion that the greater the inequality in length 

 between the pistil and the set of stamens, the pollen 

 of which is employed for its fertilisation, by so much 

 is the sterility of the union increased. There are no 

 exceptions to this rule. To understand what follows 

 the reader should look at Tables 23, 24 and 25, and 

 to the diagram Fig. 10, p. 139. In the long-styled form 

 the shortest stamens obviously differ in length from 

 the pistil to a greater degree than do the mid-length 

 stamens; and the capsules produced by the use of 

 pollen from the shortest stamens contain fewer seeds 

 than those produced by the pollen from the mid- 

 length stamens. The same result follows with the 



