1C>8 F. W. C. Aresehoug. 



extension, is, as I have already often tried to show, a very common occurrence. 

 Whether R. fissus could arise from R. suberectus, on the Scandinavian 

 peninsula, as I before (page 27) supposed, or if it immigrated here by way of 

 Denmark, is a question which may not be easy to answer. Yet now it seeins 

 lo me, that the latter supposition has the greater probability. For, just the 

 fact that I betöre mentioned in support ot an opposite opinion, viz, that in 

 Norway intermediate forms are to lie found between this subspecies and its 

 paren t species, has afterwards led me to the opinion, that R. fissus has immi- 

 grated here from abroad, like R. sulcatus. and that intermediate forms, in 

 somewhat the same circumstances as that, under which the typical subspecies 

 has aiisen, are here developed from R. suberectus. For although the possi- 

 bility of a developement of intermediate forms also exists within the area. 

 where the new species has arisen, since the outward circumstances in 

 different plaees of an area may be rather unlike, it is, all the same, hardly 

 probable that they could have existed there for long (pag. 109). • As also this 

 subspecies occurs just outside the boundaries of our country, viz, on the 

 .Jutlandic peninsula and the east coast of Seland, the possibility of its spreading 

 itself along the west coast of our country is apparent. 



The reasons in support of the opinion, that R. suberectus is the parent 

 species of all the other Suberecti, and that it is developed from sorae form of 

 R. corylifolius, in the colder parts of western Asia, have already been stated 

 (page 26 and 105). Several years ago, 1 tried to combat the opinion, that this 

 species is a hybrid of R. fruticosus and idseus (Journ. of Bot. 1873, page 109). 



Sect. IV. IdföObatUS, Focke, Syn. Rub. Germ. pag. 97. 



26. R. idaeus L. Fl. Suec. II, 446; Lindeb. Herb. Rub. Scand., n. 1; 

 var. maritimus, n. 2; var. integrifolius, n. :>. 



This species is much morc common in our country than any where eise 

 in Europé, wiih the exception of the eastern part of this continent. It seems 

 to have a preference for a northerly extension (page 24) and belongs, without 

 doubt, to the preglacial Hora of Europé. 



Belbre I commence any examination of the possible or probable origin of 

 i lus species, we will examine its changes in our country. Here, as elsewhere, 

 it. retains its typical character pretty well, and has little inclination to varv, 

 as one mighi expeci from a so comparatively old species. Var. simplicifolius, 

 Blytl (II. Leesii, Bab.) is. however, a greatly diverging form. This peculiar form 



