152 HETEEOSTYLED TEIMOEPHIC PLANTS. Chap. IV 



ones even more sterile than they otherwise would hare 

 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. 



Table 23. — Long-styled Form. 



