The portrait which forms the frontispiece is a reproduction of a
photograph taken by Professor F.E. Lloyd and Dr. W.A. Cannon during the
visit of Professor de Vries at the Desert Botanical Laboratory of the
Carnegie Institution, at Tucson, Arizona, in June, 1904.


D. T. MACDOUGAL.
December 15, 1905.



CONTENTS

A. INTRODUCTION.

LECTURE PAGE

I. Descent: theories of evolution and methods of investigation. 1
The theory of descent and of natural selection. Evolution and
adaptation. Elementary species and varieties. Methods of scientific
pedigree-culture.

B. ELEMENTARY SPECIES.

II. Elementary species in nature. 32
_Viola tricolor_, _Draba verna_, _Primula acaulis_, and other
examples. _Euphorbia pecacuanha_. _Prunus maritima_. _Taraxacum_ and
_Hieracium_.