The American Midland Naturalist 



PUBLISHED BI-MONTHLY BY THE UNIVERSITY 

 OF NOTRE DAME, NOTRE DAME, INDIANA. 



VOL. III. JULY, 1914. NO. 10. 



NOTES ON SEEDLINGS. 



(With 7 Plates.) 



BY RICHARD VOGT. 



I. — Cardamine Douglassii. 



The following is a chronological table of the nomenclature 

 of this species. 



CARDAMINE (Tourn.) L. Sp. PI. 456, 1753. 



Cardamine Douglassii Britt. Trans. N. Y. Acad. vSci. 9:8, 



Arabis rhomboidea, var. purpurea. Torr. Am. Journ. Sci. 

 6:44, 1882. 



Cardamine purpurea. Cham. & Schlecht. Linneaea i, 1824. 



Arabis Douglassii Torr. T. & G. Fl. N. A. 1:83, 1838 as a 

 synonym. 



During the past spring the young plants were closely watched 

 with the view of determining which part of the seedling formed the 

 well-know^n tuber of the mature plant. The development of the 

 seedling takes place as follows. 



The cotyledons are hypogeal and remain for some time en- 

 veloped in the seed coat. The hypocotyl is short and of a conical 

 shape terminating below in the primary root (Plate IV). The 

 epicotyl in very young seedlings is short, erect and of small 

 diameter. It gives rise at first to a single cordate long petioled 

 primary leaf and later to form one to four secondary leaves arising 

 in close proximity to the first one. When the second leaf appears 

 the epicotyl begins to increase in diameter and secondary roots are 

 given off, usually from the axils of the cotyledons but occasion- 

 ally from other points on the epicotyl (Plates IV. and V). 

 The epicotyl itself continues to increase markedly in thickness 

 until it becomes a globose tuber and at the same time it inclines 



