]62 



Plttosporum ramifiorum. 



In the earliest stadia of development of the ovide the bud 

 was sliced. The smallest ovules which were examined often 

 contained an archespore, which is surrounded by several cell- 

 layers. In this stadium nothing is yet to be seen of integu- 

 ments. Figure 1 represents an ovule with an archespore in 

 which several chromosomes are visible. 



In somewhat older stadia sporemothercells, tetrads and grow-' 

 ing embryosacs are found. The sporemothercell is pictured in 

 figure 2. It has a very large nncleus with a large nucleolus. 

 The nucellus which surrounds the sporemothercell has a thick- 

 ness of one cell. The archespore was surrounded by more cell- 

 layers, therefore cells must have degenerated by pressure of 

 the sporemothercell. The integument has already developed and 

 has a thickness of many cells. The ovule has grown to be 

 anatropous. 



Figure B shows a tetrad in which a cell-division is visible. 

 The cells of the tetrad lie in a row. The second cell from 

 below is the biggest. This was the case with many tetrads 

 and this cell is still present when the other cells are already 

 degenerating. It is probable therefore that this cell develops 

 into the embryosac. In many cases of this stadium the integu- 

 ment had grown over the nucellus. 



The development of the embryosac is pretty normal. Figure 4 

 demonstrates a binucleated embryosac. The cells of the nucellus 

 have degenerated by pressure of the developing embryosac. 

 Round the fullgrown embryosac nothing is left of the nucellus 

 but a few remnants of degenerated cells. By this the egg and 

 the synergids are lying against the micropyle. This is clearly 

 visible in figure 6. The fullgrown embryosac is long and curved 

 (figure 5). In the sections I made the antipodes had very much 

 degenerated or were not to be found at all. In the same sec- 

 tions egg, synergids and polar nucleus were very clearly shown. 

 Hence it is probable that in the fullgrown embryosac of Pitto- 



