THE CONTINENTAL FLORA OF SOUTH SWEDEN 331 



other things it must be proved that seeds capable of germination exist at the 

 time when the birds are supposed to spread them. 



The occurrence of Ranunculus illyricus on Oland is of a quite different nature 

 to those of Plantago tenuiflora and Bassia. 



It is not rare in the central and especially in the southern part of the island. 

 Its mode of occurrence there has been treated above (p. 292). The frequency of 

 the species varies a good deal with different years; and the variations are clearly 

 connected with the question how far the state of the weather is favourable to a 

 xerothermous, heliophilous plant. The flowering seems to vary very much. In 

 certain summers flowering individuals are very scarce, while on the other hand 

 sterile individuals may give a silver gray hue to wide areas through their leaves. 

 The fructification seems often to fail (cf. Erikson 1898). 



In relation to Plantago tenuiflora there is here the important difference that 

 the plant has a capacity of regenerating vegetatively in a very effective manner. 

 Each old individual developes germ-buds at the end of subterranean runners, and 

 in the next vegetative season each germ-bud gives rise to a new individual. Thanks 

 to the vegetative regeneration, therefore, Ranunculus illyricus is able to survive 

 even years unfavourable to flowering and fructification. 



With regard to such a species, therefore, we have not far to look for the 

 relic theory. 



Several species with remarkably isolated occurrences in South Sweden are 

 equipped to survive long and also to some extent to propagate in the vegeta- 

 tion. Adonis vernalis has a considerably powerful subterranean system, from 

 which a great number of vegetative-floral sprouts rise during every vegetative 

 season. As the subterranean stock of the older individuals gradually branches off, 

 new individuals are created. The case would seem to be similar concern- 

 ing Stipa pennata, Oxytropis campestris and pilosa, Pulsatilla patens and pratensis 

 (cf. Johansson 191 2), Anemone silvestris, and Asperula tinctoria. The view that 

 these species are remains of an ancient, more xerothermous flora should find a 

 certain support in this feature of the organization of species. 



Here the Pontic — South and Central European Poa bulbosa may be called to 

 mind. Along the coast of south-eastern Sweden it has a branch of distribution, 

 projecting strongly towards the north from its Central European distribution area. 

 This branch might be connected with the capacity of the species of vegetative 

 propagation. In South Sweden it is extremely rare as non viviparous. 



As has before been cursorily mentioned, some steppe species which reach 

 their north-western distribution-limits in south-eastern Sweden have one or more 

 isolated occurrences farther west, viz. in south-eastern Norway, in the country 



