Jan., 1903.] Claytonia virginica. 351 



grows verj- rapidly and gives rise to the very large cotyledon 

 (Fig. 19). This cotyledon grows very rapidly and curves into 

 almost a complete circle (Fig. 22). The inner point of growth 

 makes very little increase in size and forms the inner rudimentary 

 cotyledon, which now appears as a small projection almost at 

 right angles to the large cotjdedon (Figs. 19, 20, 21 j. 



The plumule originally stands at the upper end of the axis of 

 the embryo (Fig. 18), but with the development of the large 

 cotyledon it is pushed to one side, so tha^ in the older stages it 

 appears as a lateral plumule (Figs. 19, 20, 21 ). 



The development of the calj-ptrogen begins in the dermatogen 

 and in the cells just above the suspensor ( Fig. 19^), and gradu- 

 ally extends across the tip of the embrj'o. The root cap is formed 

 in the usual manner, by transverse division of cells in this layer, 

 and about this time the suspensor begins to disappear. 



SUMMARY. 



1. Normally four megaspores and two tapetal cells are formed, 

 the lower megaspore cell forming the embryo sac in the usual 

 manner. 



2. The first five or .six divisions in the formation of the 

 embryo are quite regular, but the succeeding divisions are very 

 irregular. 



3. The suspensor is at first filamentous, but becomes ma.ssive 

 by longitudinal divisions. It does not contribute to the forma- 

 tion of the tissues of the root-tip. 



4. Onl}- one cotyledon develops and it becomes very large ; 

 the other cotyledon remains rudimentary and gives the mature 

 embryo the appearance of a monocotjd. 



I wish to express my thanks to Professor J. H. Schaffner, of 

 the Ohio State Universit}-, for valuable suggestions in the com- 

 pletion of this study. I also wish to express my thanks to three 

 of my former students in DePauw University, Mr. J. W. Little, 

 Miss Nellie Inwood and Miss Helen Powell, for valuable material 

 and preparations. 



