CONTENTS 



A. Introduction. 

 Lecture Page 



I. Descent : theories of evolution and methods 



of investigation 1 



The theory of descent and of natural se- 

 lection. Evolution and adaptation. 

 Elementary species and varieties. Meth- 

 ods of scientific pedigree-culture. 



B. Elementary Species. 



II. Elementary species in nature ... 32 

 Viola tricolor, Draba verna. Primula 

 acaulis, and other examples. Euphorbia 

 Ipecacuanha. Prunus maritima. Taraxa- 

 cum and Hieracium. 



III. Elementary species of cultivated plants. 63 

 Beets, apples, pears, clover, flax and coco- 

 nut. 



IV. Selection of elementary species ... 92 



Cereals. Le Couteur. Running out of 

 varieties. Rimpau and Risler, Aveiia fa- 

 tua. Meadows. Old Egyptian cereals. 

 Selection by the Romans. Shirreff. Hays. 



C. Retrograde Varieties. 



V. Characters of retrograde varieties . . 121 

 Seed varieties of pure, not hybrid origin. 

 Differences from elementary species. 

 Latent characters. Ray-florets of com- 

 xiii 



