2 MR. R. H. COMPTON: AN INVESTIGATION OF THE 
Page 
Part B. SUMMARISED INFORMATION .........,‚.............. 65 
Summary [48ї.......................................... 65 
Introductory... 0.6. ccc cece eae 65 
Summary List (with ШштЧех).......................... 68 
Summaries of the different Groups ........................ 75 
Part C. GENERAL DISCUSSION .............................. 89 
Introductory ........... cece en 89 
The Nature of the Нуросоёу] ............................ 90 
Hypogeal and Epigeal Сегпіпайоп....................... 91 
The Epicotyl in the Viciee .............................. 93 
The Level of the Transition .............................. 96 
The Level of Transition and the Mature Habit .............. 98 
The Level of Transition and Phylogeny .................... 99 
The Туре of Symmetry .................................. 100 
Plumular Traces in Hypocotyl and Кооё.................... 101 
Теїтатсһу...................... te e beeen eee 104 
Reduction of the Number of Protoxylems .................. 105 
Trarehy oo. cee eee hehe 106 
Other Types of Бушшеїту................................ 108 
The Relationships of the Types of Symmetry ............... 109 
The Size of the Seedling ................................ 109 
The Primitive Habit ...................... cee eee 116 
Summary and Conclusions ......... ....................... 116 
Bibliography 22.6.0... cee eens 1i8 
Explanation of the РЇ1а{ез.................................... 120 
INTRODUCTION. 
Tur investigations of Seedling Anatomy published during the Nineteenth 
Century were largely descriptive ; their object was the establishment of 
morphological criteria and definitions of such concepts as the collet, 
hypocotyl, &c. A variety of types, culled from widely-separated groups of 
plants, were usually selected for examination ; with the result that a broad 
but vague knowledge of the anatomical tendencies of seedlings was obtained. 
During the past decade a new and vigorous interest has been aroused in the 
morphology and anatomy of juvenile forms; the stimulus being the expec- 
tation that a study of ontogeny will yield, in plants as in animals, valuable 
phylogenetic data. In the Pteridophyta this hope has been amply justified ; 
but in the Phanerogams, with certain notable exceptions, the results have so 
far been meagre and disappointing. 
It has, however, been realised that the eclectic method of investigation of 
the Nineteenth Century must give place to the detailed study of the 
phenomena within systematically restricted groups of plants. In this way a 
great mass of information has been acquired from several circles of affinity. 
Thanks to the researches of T. G. Hill and E. de Fraine (1908-1910) and 
