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Show 104 HETEROSTYLED DIMORPHIC PLANTS. CHAP. III. fertilised during several successive generations sometimes 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 angustijolia.-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 ef the leaves, that the two have been considered by several eminent botanists-for instance, Bentham-as mere varieties. But, as we shall presently see, good evidence can be assigned for. ranking th~m as distinct. Owing to the doubts on this head, I tned whether the two would mutually fertilise one another. rrwelve short-styled. flowers of P. angustijolia were legitimately fertilised with pollen from. long-styled plants of P. officinalis (which, as we have JUSt seen, are n1oderately self-fertile), but they did not produ~e a single fruit. Thirty-six long-styled flowers of P. angu.stijolia were also illegitimately fertilised during two seasons with pollen from the long-sty led . P. officinalis, but all these flowers dropped of! ~nllllpregnated. Had the plants been mere vaneties 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 fo~lowing table (20). Therefore P. officinalis and a~gus~2- folia appear to be good and distinct species, In CHAP. III. PULMONARIA ANGUSTIFOLIA. 105 conformity with other important functional differences between them, immediately to be described. The long-sty led and short-sty led flowers of P. angustijolia differ from one another in structure in nearly the same manner as those of P. o.fficinalis. But in the accompanying figure a slight bulging of the corolla Fig. 6. Long-styled form. Short-styled form. PULMON ARIA ANG USTIFOLIA. in the long-styled form, where the anthers are seated, has been overlooked. My son William, who examined a large number of wild plants in the Isle of Wight, observed that the corolla, though variable in size, was generally larger in the long-styled flowers than in the short-sty led ; and certainly the largest corollas of all were found on the long-sty led plants, and the smallest on t~e short-sty led. Exactly the reverse occurs, acc? r~Ing to Hildebrand, with P. officinalis. Both the p1stils and stamens of P. angustifolia vary much in length; so that in the short-styled form the distance between the stigma and the anthers varied from 119 to 65 divisions of the micrometer, and in the longstyled from 115 to 112. From an average of seven |