104 HETEROSTYLED DIMORPHIC PLANTS. CHAP. Ill 



iertilised during several successive generations some- 

 times become more self-fertile ; and this may have 

 been the case with my stock of the present species 

 of Pulmonaria ; but in this case we must assume 

 that the long-styled plants were at first sufficiently 

 fertile to yield some seed, instead of being absolutely 

 self-sterile like the German plants. 



Pulmonaria angustifolia. Seedlings of this plant, 

 raised from plants growing wild in the Isle of Wight, 

 were named for me by Dr. Hooker. It is so closely 

 allied to the last species, differing chiefly in the shape 

 and spotting of the leaves, that the two have been con- 

 sidered by several eminent botanists for instance, 

 Bentham as mere varieties. But, as we shall presently 

 see, good evidence can be assigned for ranking them 

 as distinct. Owing to the doubts on this head, I tried 

 whether the two would mutually fertilise one another. 

 Twelve short-styled flowers of P. angustifolia were 

 legitimately fertilised with pollen from long-styled 

 plants of P. officinaUs (which, as we have just seen, are 

 moderately self-fertile), but they did not produce a 

 single fruit. Thirty-six long-styled flowers of P. 

 angustifolia were also illegitimately fertilised during 

 two seasons with pollen from the long-styled P. 

 oflicinalis, but all these flowers dropped off unim- 

 pregnated. Had the plants been mere varieties of 

 the same species these illegitimate crosses would 

 probably have yielded some seeds, judging from my 

 success in illegitimately fertilising the long-styled 

 flowers of P. officinalis ; and the twelve legitimate 

 crosses, instead of yielding no fruit, would almost 

 certainly have yielded a considerable number, namely, 

 about nine, judging from the results given in the fol- 

 lowing table (20). Therefore P. officinalis and angusti- 

 folia appear to be good and distinct species, in 



