Nilsson: Plant-Breeding in Sweden 



291 



fixed and with the aid of the auxiHary 

 associations whom we serve, we may sa}^ 

 that the Institute of Svalof has reached 

 its essential and pecuHar goal, and that 

 it has attained for itself a memorable 

 and incontestable place in the history of 

 plant improvement. Following its ex- 

 ample, all analogous contemporary oper- 

 ations have successively passed from 

 selection in mass to the utilization of the 

 qualities of hereditary character, studied 

 on an isolated plant, although some- 

 times under different names, such as 

 "individual selection," "selection by 

 families," etc. Separate culture and 

 separate judging have also been, and still 

 are, conditions necessary to the practical 

 application even of discoveries made 

 later concerning the value of different 

 qualities as mobile, hereditary units. 



I would certainly not wish to be 

 understood as saying that propagation 

 of separate plants had not previously 

 been made by cultivators like Shirreff, 

 Vilmorin and Hallet. But it is certain 

 that not one of them, not even Vilmorin, 

 had ever realized such great possibilities 

 of this simple procedure, as we had dis- 

 covered and applied in practice here 

 at Svalof 20 years ago. 



Furthermore, their experiments in this 

 direction were, at the beginning of our 

 experience, so completely forgotten and 

 ignored in practice, that it was necessary 

 for us, as I have already said, to discover 

 the fact anew. 



The reader may well ask of what 

 nature are all these little elementary 

 species, which have allowed the old 

 material to be sorted out into inde- 

 pendent new sorts ? Do they come from 

 mutations, from natural cross-polli- 

 nation, or from both together? 



It is a fact well authenticated at 

 Svalof that mutations appear from 

 time to time in our cultivated plants. 

 Furthermore, we have found that spon- 

 taneous fecundation is much commoner 

 than we had supposed. But it must not 

 be imagined that we can discover with 

 certainty, in each particular case, the 

 origin of all the forms — and anyway, the 

 knowledge of how they originated does 

 not trouble our practical work, for which 

 the fact of their existence is sufficient. 

 Finally, it must be noted that the sig- 



nificant results furnished by diverse 

 methods of origin are the same' in the 

 two cases, that is to say, they lead to 

 the possession by each group of a multi- 

 tude of systematic unities, differing 

 from each other in the way their char- 

 acters, often few in number, are com- 

 bined. They are all what have been 

 called "minute species" or "elementary 

 species." Mr. Johannsen, who later 

 examined them carefully, has described 

 them as "pure lines." Here we have 

 retained for them, for practical reasons, 

 the English name of "pedigrees." 



IN CROSS POLLINATION. 



Although we did our first work of 

 this kind with self -pollinating species 

 (wheat, barley, oats, peas, vetch), we 

 have later, in dealing with rye, clover, 

 forage grasses, beets, etc., had occasion 

 to convince ourselves that the existence 

 of these small species, quite analogous, 

 is clear in plants which are not self- 

 fertilized. With these, of course, we 

 do not find the pure lines immediately 

 upon isolation. They require syste- 

 matic treatment diiring some years, to 

 offer a satisfactory degree of purity and 

 stability, which even then can never 

 become so perfect as among self- 

 fertilized species. But it is already 

 proved that by the aid of such forms we 

 can reach the same practical results as 

 by the aid of the elementary species. 

 The extension of Svalof Institute has 

 as its principal object to make the 

 treatment of these groups of crossed 

 lines more intense by the fixation of the 

 forms, followed by their careful valua- 

 tion. 



Among the means of securing new 

 forms of cultivated plants, I must also 

 also mention artificial hybridization. 

 About 20 years ago, when w^e were 

 entirely occupied in profiting from the 

 precious forms which an exploration 

 of our old varieties had given us, we had 

 no chance to study this method seriously. 

 Furthermore, the extended experiments 

 with cereal-hybridization which we made 

 some years later (1897-9) did not give 

 encouraging results. Nevertheless, the 

 fall wheat Svalof Extra Squarehead II, 

 finally so famous, dates from that first 

 series of crossings. 



