1914] COULTER & LAND—MONOCOTYLEDONY 519 
the early and vigorous development of the first leaf in Monocotyle- 
dons is probably associated with checking the growth of the adja- 
cent cotyledonary primordium. 
Incidentally the late appearance of the stem as an organized 
structure probably enters into the explanation of the fact that the 
stem is the most advanced organ of the body in structure, as vascu- 
lar anatomy has indicated repeatedly. In any event, the cotyle- 
donary strands and first leaf strands organize the cotyledonary 
plate, which in turn gives rise to the root poles, and later determines 
the character of the stem cylinder. 
The main thesis of this study of cotyledony, however, is to 
release it from its rigid morphological categories, by showing that 
the cotyledonary apparatus is always the same structure, arising in 
the same way, and varying only in the details of its final expression. 
UNIVERSITY OF CHICAGO 
EXPLANATION OF PLATES XXVIII AND XXIX 
Fics. 2-14.—Monocotyledonous embryo of Agapanthus umbellatus: figs. 
2-13, transverse sections beginning just above the cotyledonary sheath and 
ending in the cotyledonary plate (the sequence of numbers indicates the 
sequence of sections); fig. 14, a diagrammatic reconstruction of the sections; 
Fics. 15-29.—Dicotyledonous embryo of Agapanthus umbellatus: figs. 
15-28, transverse sections beginning just above the cotyledonary sheath and 
ending in the cotyledonary plate (the sequence of numbers indicates the 
sequence of sections); fig. 29, a diagrammatic reconstruction of the sections; 
X 14. 
