g.54 RECIPKOCAL DIMORPHISM Cuap. VIII. 



generally amiiliilatcs the effect of the foreign pollen; so it is 

 with the pollen of the several forms of the same species, for 

 legitimate pollen is strongly prepotent over illegitimate pollen, 

 when botii are placed on the same stigma. I ascertained this 

 by fertilizing several flowers, first illegitimately and twenty- 

 four hours afterward legitimately, with pollen taken from a 

 peculiarly-colored variety, and all the seedlings were similarly 

 colored; this shows that the legitimate pollen, though applied 

 twenty-four hours subsequently, had wholly destroyed or pre- 

 vented the action of the previously-applied illegitimate pollen. 

 Again, as in making reciprocal crosses between the same two 

 species, there is occasionally a great difference in the result, so 

 the same thing occurs Avith trimorphic plants ; for instance, 

 the mid-styled form of Lythrum salicaria Avas illegitimately 

 fertilized with the greatest case by pollen from the longer sta- 

 mens of the short-styled form, and yielded many seeds ; but 

 the latter form did not yield a single seed when fertilized by 

 the longer stamens of the mid-styled form. 



In all these respects and in others which might have been 

 adduced, the forms of the same imdoubted species when ille- 

 gitimately united behave in exactly the same manner as do two 

 distinct S[)ecics wheii crossed. This led me carefully to ob- 

 serve during four years many seedlings, raised from several 

 illegitimate unions. The chief result is that these illegitimate 

 ])lants, as they may be called, are not fully fertile. It is possi- 

 ble to raise from dimorphic species both long-styled and short- 

 styled illegitimate plants, and from trimorphic plants all three 

 illegitimate forms ; these can then be properly united in a le- 

 gitimate maimer. When this is done, there is no apparent 

 reason why they should not yield as many seeds as did their 

 parents when legitimately fertilized. But such is not the case ; 

 they are all infertile, but in various degrees; some being so 

 utterly and incurably sterile that they did not yield during 

 four seasons a single seed or even seed-capsule. The sterility 

 of these illegitimate plants, when united with each other in a 

 legitimate manner, may be strictly compared with that of hy- 

 brids when crossed inter sc. When on the other* hand a hybrid 

 is crossed with either pure parent-species, the sterility is usu- 

 ally much lessened : and so it is when an illegitimate plant is 

 fertilized by a legitimate plant. In the same manner as the 

 sterility of hybrids does not always run parallel with the difii- 

 culty of making the first cross between the two j^arent-species, 

 so the sterility of certain illegitimate plants was usually great, 



