AND TRIMORPHISM. , 299 



vvliolly destroyed or prevented the action of the previously 

 applied illegitimate pollen. Again, as in making recipro^ 

 cal crosses between the same two species, there is occa- 

 sionally a great difference in the result, so the same thing 

 occurs with trimorphic plants; for instance, the mid- 

 styled form of Ly thrum salicaria was illegitimately fer- 

 tilized with the greatest ease by pollen from the longer 

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

 but the latter form did not yield a single seed when fer- 

 tilized by the longer stamens of the mid-styled form. 



In all these respects, and in others which might be 

 added, the forms of the same undoubted species, when 

 illegitimately united, behave in exactly the same manner as 

 do two distinct species when crossed. This led me carefully 

 to observe during four years many seedlings, raised from 

 several illegitimate unions. The chief result is that these 

 illegitimate plants, as they may be called, are not 

 fully fertile. It is possible to raise from dimorphic species, 

 both long-styled and short-syled illegitimate plants, and 

 from trimorphic plants all three illegitimate forms. These 

 can then be properly united in a legitimate manner. AVhen 

 this is done, there is no apparent reason why they should 

 not yield as many seeds as did their parents when legiti- 

 mately fertilized. But such is not the case. They are all 

 infertile, in various degrees; some being so utterly and in- 

 curably 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 legiti- 

 mate manner, may be strictly compared with that of 

 hybrids when crossed i7iter se. If, on the other hand, a 

 hybrid is crossed with either pure parent-species, the ster- 

 ility is usually much lessened: and so it is when an illegiti- 

 mate plant is fertilized by a legitimate plant. In the 

 same manner as the sterility of hybrids does not always run 

 parallel with the difficulty of making the first cross between 

 the two parent-species, so that sterility of certain illegiti- 

 mate plants was unusually great, while the sterility of the 

 union from which they were derived was by no moans 

 great. With hybrids raised from the same seed-capsule 

 the degree of sterility is innately variable, so it is in a 

 marked manner with illegitimate plants. Lastly, mnny 

 hybrids are profuse and persistent flowerers, while ot^:-r 



