148 BOTANICAL GAZETTE [august 



regards as of the deepest significance, not only in practical plant breeding, but 

 chiefly in reference to evolutionary doctrine. To develop the importance of 

 NiLSSOx's work clearly, the author considers the general topic in four sections. 

 The first is a historical sketch of the ''Different principles in the breeding of 

 cereals," in which the contributions of LeCouteur, Shirreff, Hallett, 

 Hays, and Vox Lochow are considered. The first two worked upon the prin- 

 ciple of a single initial selection and subsequent rapid multiplication without 

 further selection, in this sense being the precursors of the Svalof method. Then 

 came the domination of Hallett, whose principle was accepted by German 

 breeders, and seems to govern them to this day. Its two essential features are 

 the initial choice, and the slow and gradual improvement by selection. With 

 great force the author shows that all depends upon initial choice, subsequent 

 selections only serving to isolate the deviating types; and these " initial choices" 

 were never numerous. It is significant that Darwin's theory of natural selection, 

 based inferentially upon artificial selection, was developed at a time when this 

 so-called "German method" prevailed, and the emphasis was being laid upon the 

 continuous selection rather than upon the initial choice. The second section 

 describes *'The Swedish Agricultural Experiment Station at Svalof." It began 

 with the German conception of plant breeding, but soon changed to its present 

 ideas. The results have shown that ordinary cultivated varieties of cereals are 

 not pure, but are mixtures of well-defined and very numerous types; that when 

 there is so great a range of types for selection, there is only loss of time in gradual 

 amelioration by so-called methodical selection or in hybridization to secure 

 new varieties. The third section presents "The Svalof method of producing 

 improved races," being a detailed account of the method of selection developed 

 by NiLssoN and his staff. Elementary forms are distinguished by definite "marks" 

 (botanical characters) that have been found to be associated with certain indus- 

 trial qualities. The selection is made only once, and the form is found to be 

 quite uniform and constant, with the exception of accidental hybrids, which, 

 however, also yield constant and pure races after repeated selection. The high 

 variability which is commonly attributed to the ordinary varieties of cereals consists 

 only in the differences among the constituents of the mixtures. The fourth section 

 is "A criticism of the principles of continuous selection," and is a most effective 

 analysis of the bearing of Nilsson's work upon the question of the origin of 

 species by natural selection or by mutation. According to the author, the idea 

 of unit-characters has changed the whole point of view, and the theor>^ of mutation 

 is supported by the general occurrence of elementary species and their constancy, 

 by a comparison of the value of fluctuating variability and mutability among 

 cereals, and by the researches of Nilsson. He goes so far as fo claim that 

 "the victory of the theory of a saltatory origin of species can no longer be doubted." 

 The third general topic is "On corn breeding," and it is most interesting to 

 read the comments of a trained European plant breeder upon the methods of 

 breeding used in connection with this dominant cereal of the United States. 

 The real breeding of com began about ten years ago, with the discovery of the 



