420 
Lawson .— The Gametophytes and 
Fig. n. A section of a pollen-tube taken just eleven months later than that shown in Fig. io. 
Here the body-cell has descended into the tube and is situated near the tip. Its nucleus is very 
much enlarged in preparation for mitosis. June 19. 
Fig. 12. A longitudinal section of a body-cell, showing the result of the division of the body- 
nucleus. The two male nuclei appear in sectional view to be of unequal size, but lie freely within 
the cytoplasm of the body-cell with no membrane separating them from one another. June 15. 
Fig. 13. An outline drawing of a longitudinal section of an ovule. 
Fig. 14. A transverse section of the megasporangium, showing the functional megaspore-mother¬ 
cell embedded in the tapetum. It will also be seen that the sporangium is connected with the 
integument at opposite sides of the broadest diameter, giving strength and support to the sporangium 
region. June 4. 
Fig. 15. A longitudinal section of a megasporangium, showing the position of the large 
megaspore-mother-cell completely surrounded by two or three layers of tapetal cells. June 4. 
Fig. 16. A longitudinal section to show the relative size of the megaspore-mother-cell to the 
surrounding tapetal cells. June 3. 
Fig. 17. A megaspore-mother-cell with the nucleus enlarged and preparing for the reduction 
division. May 12. 
Fig. 18. The same at a later stage, showing the chromatin in the form of a tangled spireme and 
the nuclear cavity considerably enlarged. May 12. 
Fig. 19. The same at a slightly later stage, with the chromatin threads more slightly differentiated. 
June 3. 
Fig. 20. The same with the chromatin threads thicker, shorter, and more evenly distributed 
through the nuclear cavity. June 3. 
Fig. 21. A slightly later stage of the same, with the chromatin in the form of thick granular 
threads. June 3. 
Fig. 22. The same with the granular chromatin threads still more shortened and thickened. 
June 3. 
Fig. 23. The same with the chromatin threads so shortened and thickened that this granular 
nature is much less evident. Definite chromosomes are now formed. June 3. 
Fig. 24. A later stage of the same, showing the double nature of the chromosomes. June 3. 
Fig. 25. A megaspore-mother-cell at the time of the formation of the reduction spindle and 
showing the form of the heterotype chromosomes. June 4. 
Fig. 26. A megaspore-mother-cell, showing the mature reduction spindle with the chromosomes 
at the equator. June 4- 
Fig. 27. A reduction spindle with the heterotype chromosomes facing the equatorial plate. 
June 4. 
Fig. 28. A transverse section of a megaspore-mother-cell with the heterotype chromosomes at 
the equatorial plate. June 4. 
Fig. 29. A megaspore-mother-cell in the later phase of the reduction division, with the 
chromosomes at the poles of the spindle, and before the organization of the daughter-nuclei. 
June 4. 
Fig. 30. The same a little later, with the daughter-nuclei organized, and the chromosomes very 
much vacuolated and giving a reticulated appearance. There is no trace of a cell-wall separating 
the daughter-nuclei from one another. June 4. 
Fig. 31. A mother-cell, showing the simultaneous division of the daughter-nuclei. The twin 
spindles lie one above the other with the chromosomes, which are clearly reduced in number from 
the equatorial plates. June 4. 
Fig. 32. The result of the second division of the mother-cell. Here it will be seen that 
cell-walls are formed after this division, and, as a result of this, these cells constitute an axial 
row. But in consequence of there being no cell-wall formed after the first division, and two 
cell-walls formed after the second division, we find the middle cell of the axial row containing two 
free nuclei, and the two end cells one each. June 4. 
Fig. 33. A somewhat later stage of the same, showing the definite cell-walls separating the 
two end cells of the axial row from the middle cell, and the latter containing two free nuclei. It 
will be noted also that starch is much more abundant in the basal cell of the axial row than in the 
other two. June 4. 
Fig. 34. A still later stage of the same, showing a shifting of the two free nuclei of the middle 
