364 Descendenz und Hybriden. 



From the experiments reported in details in the paper it 

 becomes evident, that at present some of the north 

 European species of Riibiis are in a state of mutation; 

 such is the case with Riibus vlllicaulis Koehl., var. parvuliis 

 Hülsen, R. polyauthemiis Lindeb , R. insiilaris F. Aresch., R. 

 vestitiis Weihe and R. siiberectiis Anders. It is beyond doubt, 

 that continued investigations will point out a rather large 

 number of mutating species. The mutations observed differ 

 mostly in more than one respect from the parent-species. In 

 the case in which it has been possible to prove the constancy, 

 it has been absolute. The coefficient of mutation seems to 

 change between 1 and 3 per cent. 



F. Areschoug's theory, that the producing of species 

 in the genus Riibiis is going on in sudden appearances of new 

 forms, has then now been proved through these experiments. 

 Together with the production of species through mutation 

 another production of species is tobe found in Riibus, 

 viz. through hybridisation. The experiments show, that 

 s e V e r a 1 Riibus- species produce fertile hybrids; even 

 by Crossing species which systematically are rather remote to 

 each-other (R. caesliis L. and R. thyrsoideiis Wimm.). 



In some cases is has been found that the pollen of the 

 primary hybrid is better (more fertile) than that of one of 

 the parents (R. caesiiis X acuminatus better than R. aciiml- 

 natiis Lindbl.; R. caesius X thyrsoideiis better than R. thyr- 

 soideiis) ; and in accordance to that the fructification of the 

 hybrids is better than that of the one parent. The primary 

 hybrids are mostly intermediate to the parents and new cha- 

 racters have not been found. 



Through self-fertilisation the primary hybrids 

 produce an offspring which is highly polymorph, 

 the Single individuales differing with regard to very important 

 respects as well from their brothers and sisters as from their 

 parents. The differences between the individuals of the offspring of 

 one Single primary hybrid are often so distinct, that it should 

 be possible to place them in different systematical groups of 

 the genus. Some of the off spring are wholly fertile, 

 otherwholly sterile and other moreor less inter- 

 mediate. Also the vegetative power of the offspring 

 is very unlike, some individuals being luxuriant, other being 

 reduced to dwarf forms, which give no flowers. 



One can not explain the Polymorphismus of the offspring 

 of the primary hybrids through the Splitting of the characters 

 of the parents; it is necessary to suppose mutations 

 released through the hybridisation. These hybrid- 

 mutations are in some cases atavisms, in other progressive 

 mutations. 



The offspring of the primary hybrids is in- 

 constant, but to a rnuch inferior degree than the 

 primary hybrid; in one case more than 50 per cent were 



