Read the information in this window and then label your printed diagram that corresponds to this diagram's number. Start with diagram number 1 and continue sequentially.

The drawing on the left shows an ovule (1) containing a single megaspore mother cell (2). Its chromosome number (2N), is the same as the other cells of the sporophyte plant. The megaspore mother cell resides within the ovule that is surrounded by integuments (5) and is attached to the wall of the ovary by the funiculus (3). As the integuments grow together a threadlike opening is left between them. This opening, the micropyle (4), will provide space for the pollen tube to grow into the ovule at the time of fertilization. Notice that the megspore mother cell is surrounded by the tissue of the megasporangium (nucellus). All tissue colored green or yellow is 2N and diploid.

In the photograph, of a microscope slide preparation of the ovule, we see that the ovule nearly fills the locule surrounding it. The image also shows the cells that make up each structure that has been labeled. Again, it is worth restating that all of these cells are part of the sporophyte generation of the plant and that they are diploid (2N). You can think of the megaspore mother cell as one of the last two cell types of the sporophyte generation. Later after a series of cell divisions it will give rise to a new generation of the plant, the megagametophyte. Can you think of another cell type that also ends the sporophyte generation? I am thinking of the microspore mother cells found within the anthers. They go on to produce microspores which in term develop into microgametophytes (pollen).

Now we know that flowering plants are heterosporus. They produce two kinds of spores in two different kinds of sporangia and each spore type develops into a different kind of gametophyte.