123 



011 the subject, the author gives (p. 32) a detailed account of Ihe 

 morphology of the Potentilla-f\o\\eT, and there shows that, P. friili- 

 cosa. Hke P. bifiirca and, probably, P. dainirica too, is ,,iinperfect 

 dioecious". 



P. fniticosa on the island of Öland, however, is purely dioecious, 

 i. e., all the flowers on the same individual produce either pollen 

 alone or seed alone, irrespective of whether the suppressed sex of 

 the flower is represented by moie or less evident rudiments, or 

 not. As far as I know, this was first discovered by Professor G. 

 Lagerheim, who mentioned the fact to me in the spring of 1906. 

 My surmise is, that the same condition of thing exists in norlhern 

 Gotland — from which Vestergren, Johansson and H.\gg, in 

 1908, described the habitat of P. fruticosa — and in the extra- 

 Scandinavian localities. 



I shall give below a brief summary of the results of the ob- 

 servations respecting P. fruticosa — and, specially, its flowering — 

 that I have been able to make on the southern „alfvar' of Öland, 

 during the summers of 1906, 1907, 1909 and 1910 and in the 

 winter of 1910 — 11. 



HABITATS. 



I wish to mention the following points from Wolf's monography: 

 The place of origin of the Polenlilla-genu^ was the circum-polar 

 land of the tertiary period, and, even to-day, its chief area of distri- 

 bution is that sea-divided helt of land in the northern hemisphere 

 Ihat lies between the tropic of Cancer and the eternal ice of the 

 polar regions. At the close of the tertiary period, when the climate 

 underwent a change and the continents were mapped out, a new 

 phase began in the story of the development of the Po/en//7/a-genus: 

 some species die out: others, \vith greater capability of adaptation, 

 survive: some take other forms of development, difTerent in the 

 three continents. The now-exisling groups of species belong to the 

 two following categories: 1) Groups poor in species: the species 

 being relatively constant and showing little tendency to hybridism. 

 These — the pala?otypical — are the oldest that have survived. 



^ The ..alfvar" is an extensive limestone table-land occupying nearly the whole of 

 the south of the island of Öland, boasting a wealth of wild, almost dwarfed species, 

 hut almost incapablc of cultivation. There is also a smaller tract of the same 

 character in the middle of the island, near the town of Borgholm. 



