Chap. IX.] AND TRIMORPHISM. 31 



when fertilised 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 re- 

 sult 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-styled 

 illegitimate plants, and from trimorphic plants all three 

 illegitimate forms. These can then be properly united 

 in a legitimate manner. When this is done, there is no 

 apparent reason why they should not yield as many 

 seeds as did their parents when legitimately fertilised. 

 But such is not the case. They are all infertile, 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 ? 

 legitimate manner, may be strictly compared with that 

 of hybrids when crossed inter se. If, on the other hand, 

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

 sterility is usually much lessened: and so it is when 

 an illegitimate plant is fertilised 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 the sterility 

 of certain illegitimate plants was unusually great, whilst 

 the sterility of the union from which they were derived 

 was by no means great. With hybrids raised from the 

 same seed-capsule the degree of sterility is innately 



