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ANNA HALL RAITT 



The embryo is formed by the division of the egg in the usual 

 way. The suspensor is short and broad, and the cells are flat- 

 tened as though they were under pressure (fig. 2, Q). It dis- 

 appears almost completely by the time the embryo begins to 

 elongate. The embryo retains its spherical shape after it is large 

 and many-celled. Soon after it elongates a groove appears in 

 the tip, and this deepens until the cotyledons are formed and 

 the stem tip appears. By this time the dermatogen has become 

 marked (fig. 3, V). 



Fig. 3. T. Microphotograph of the first division occurring in the embryo-sac. 

 U, Microphotograph of the fertilized egg just before division, with polar nuclei. 

 V, Microphotograph of the base of an embryo, showing cotyledons and der- 

 matogen. 



During the growth of the embryo, first the nucellus, then the 

 endosperm cells are used and then the inner integument begins 

 to disintegrate to furnish food for the embryo. This proceeds in 

 the integument from the outside inward. Finally, only the 

 tapetal jacket and the beak-like end of the inner integument 

 remain, the outer becoming thick and forming the only covering 

 for the seed. 



SUMMARY 



The ovule of 7. pallida has two integuments, the innermost 

 layer of the inner one being composed of tapetum-like cells which 

 persist after the integument has been resorbed. The cells of the 



