268 BOTANICAL GAZETTE [april 



ment 



Euphorbia. The outer integu- 

 rier. The obturator of E. Myr- 



sinites begins as a small outgrowth from the placenta when the 

 outer integument has grown almost half-way to the tip of the 

 nucellus. The cells of the obturator increase rapidly, the outer 

 ones becoming long and hairlike. At the time of fertilization, the 



mature 



micropyle. The long cells of this structure com 



integuments 



never grow into the nucellar tissue. The obturator gradually 



egrates 



small swellin 



form 



The 



nucellus has a long, slender tip which is surrounded by the cells of 



6 



the obturator. The caruncula is formed from the outer int 

 after the embryo has developed. A row of cells differentiates it 

 from the seed proper. This structure resembles a cap and aids in 

 loosening the seed from the placenta at the time of dispersal. 

 Schmidt (i8) finds more than one megaspore mother cell in 

 E. palustris. These are situated deep in the cells of the nucellus. 

 His account of the development of the flower agrees with that of 

 Miss Lyox (8). 



Modilewski (n) describes an unusual development of the 

 embryo sac in E. procera. The first 4 nuclei of the embryo sac are 

 arranged in the form of a cross. Two divisions result in the forma- 

 tion of 4 tetrads of nuclei. One nucleus from each group migrates 

 to the center of the sac, where the 4 unite. The mature embryo 

 sac contains an egg apparatus, 3 antipodal cells, and 2 groups of 

 3 nuclei each, lying on opposite sides of the sac. In fertilization, 

 one male nucleus fuses with the egg nucleus, and the other male 

 nucleus fuses with the quadrivalent fusion nucleus in the center. 

 The synergids, antipodals, and nuclear groups at the sides of the 

 sac disintegrate. No case of polyembryony was observed. Later, 

 Modilewski (12) described the events preceding embryo sac 

 development in E. procera. An archesporial row of 3 or 4 cells 

 was found, each ultimately containing 4 nuclei. Only one of the 

 4-nucleate cells develops into an embryo sac. Often one or more 



