17 G F. W. C. Areschoug. 



oii the Scandinavian peninsula. Of all the other forms peculiar to the Scan- 

 dinavian flora, it holds good as a general rule, that they never grow in Com- 

 pany with the species, from which they are descended. And also, if it should 

 by accident occur, that a form grows together with its parent species, it can 

 easily be reconciled with niy opinion. For if a species that has immigrated 

 here, finds a locality favourable for it, it must be able to remain, in some 

 depree unchanged. and by degrees get accustomed to the climatic surroundings. 

 When after it has gained a certain stability, it spreads to less favourable lo- 

 calities, it is not changed. If on the other hand, the same species, when it 

 first canie över here, met with' localities to which it was not accustomed, it 

 becoraes more influenced and modified by outward conditions (pages 68, 86). 



4. It is very probable, that the climatic conditions hare had the power to 

 call forth still greater changes in the immigrant brambles, the more the local 

 conditions in which they have come to live, recede from those to which they 

 were accustomed in their native country. And at the same time, it is probable, 

 that a a immigrated species could bett er succeed in resisting the climatic condi- 

 tions and in remaining unchanged, if it had come to a locality, that coincitles 

 more irifh that from whicli it had come. 



These are only a small number of facts, that I have been able to give as 

 proof of this opinion. I have already stated, that R. scanicus is developed from 

 R. Arrhenii, which however is wanting in this country. R. Arrhenii grows in 

 deep shady woods, R. scanicus, on the contrary, grows in more'open and thin- 

 ner woods consisting of smaller trees, and most often on their edges. I ' think 

 that when 11. Arrhenii came to Skåne, it settled down in such open small 

 woods, and under these unusual surroundings became more susceptible to the 

 prevailing climatic conditionss. Var. grandifolius of R. nitidus can also 

 be given as an example in this respect. 



What, however, seems to me most in support of my opinion, is, that some 

 species and forms have been able to keep themselves almost completely unchan- 

 ged, while others have changed considerably. Certainly, this can be partly ex- 

 plained thus, that the older species generally show a greater degree of stabi- 

 lity. But also many of the younger species and forms, e. g. R. Radula (page 

 125), R. pyramidalis (page 137), R. infestus (page 128), R. corylifolius, 

 *dumetorum (page 94), are without difficulty identified with the correspon- 

 ding Continental forms. 



