June, 1922] FARR — ^ MEIOTIC CYTOKINESIS OF NELUMBO 
which is the last to be traversed by the furrow. There are six spindles 
and four furrows as in Nicotiana (6), and the furrowing usually proceeds a 
little faster at the region of the junction of the three furrows, so that the 
furrowing may extend to the geometrical center of the cell before it has com- 
pletely traversed the spindles. This situation was found in a considerable 
number of cells observed. 
The mother-cell wall becomes more uniformly thickened on all sides as 
the microscope stage approaches. As noted above, the microspores when 
first formed are separated by very thin plates consisting of the two plasma 
membranes and a very thin layer of wall material. The spindle fibers are 
still quite conspicuous at this time, as was also noted by Lubimenko and 
Maige in the forms they studied (13). As the spindle fibers disappear the 
microspores slowly round up, the wall material becoming more abundant 
at the periphery at first. It is not clear whether this consists in the sweUing 
of the material already in place or in the intrusion of additional material 
from the older portions of the surrounding wall. Although the rounding- 
up process takes place more slowly than in any form which I have previ- 
ously studied, yet it is finally carried forward to the same extent as in the other 
forms. 
LITERATURE CITED 
1. Bailey, I. W. Phenomena of cell division in the cambium of arborescent gymnosperms 
and their cytological significance. Proc. Nat. Acad. Sci. 5 : 283-284, fig. i. 
1919. 
2. • . The formation of the cell plate in the cambium of the higher plants. Proc. Nat. 
Acad. Sci. 6 : 197-200, 8 figs. 1920. 
3. . The cambium and its derivative tissues II. Size variations of cambial initials 
in gymnosperms and angiosperms. Amer. Jour. Bot. 7:355-367, figs. 1,2. 
1920. 
4. . The cambium and its derivative tissues III. A reconnaissance of cytological 
phenomena of the cambium. Amer. Jour. Bot. 7 : 417-434. Pis. 26-29. 1920. 
5. . The significance of the cambium in the study of certain physiological problems. 
Jour. Gen. Physiol. 2 : 519-533. PI. i, text figs. 1-4. 1920. 
6. Farr, C. H. Cytokinesis of the pollen mother cells of certain Dicotyledons. Mem. 
N. Y. Bot. Garden 6 : 253-317. Pis. 27-29. 1916. 
7. . Cell division by furrowing in Magnolia. Amer. Jour. Bot. 5 : 379-395. Pis. 30-32. 
1918. 
8. . Quadripartition by furrowing in Sisyrinchium. Bull. Torrey Bot. Club 49:51- 
62. PI. 2. 1922. 
9. Farr, Wanda K. Cell division of the pollen mother cell of Cobaea sca?tdetis alba. Bull. 
Torrey Bot. Club 47 : 325-338. PI. 14. 1920. 
10. Gates, R. R., and Rees, E. M. A cytological study of pollen development in Lactuca. 
Annals of Bot. 35 : 365-398. Pis. 16-19. 1921. 
11. Juel, H. O. Die Kerntheilung in den PoUenmutterzellen von Hemerocallis fulva. 
Jahrb. Wiss. Bot. 30 : 205-226. Pis. 6-8. 1897. 
12. . Beitrage zur Kenntnis der Tetradenteilung III. Die Entwicklung der Pollen" 
korner bei Carex. Jahrb. Wiss. Bot. 35 : 649-656. PI. 16, figs. 28-44. 1900. 
13. Lubimenko, W., and Maige, A. Recherches cytologiques sur le developpement des 
cellules-meres du pollen chez les Nympheacees. Rev. Gen. Bot. 19 : 474-505. 
Pis. 1-5, text figs. I, 2. 1907. 
