564 Morrier AND NOTHNAGEL: CHROMOSOMES OF ALLIUM 
the polar and antipolar sides. The ends of the chromatin segments 
do not fuse into ‘‘Chromatinknoten”’ in the daughter nucleus. 
INDIANA UNIVERSITY, BLOOMINGTON 
LITERATURE CITED 
Bonnevie, K. (’11). Chromosomenstudien, III. Chromatinreifung in 
Allium Cepa (o"). Archiv Zellforschung 6: 190-253. I9QII. 
Lawson, A. A. (’11). The phase of the nucleus known as synapsis. 
Trans. Royal Soc. Edinburgh 47: 591-604. IgII. 
Mottier, D. M. (?03). The behavior of the chromosomes in the spore 
mother-cells of higher plants and the homology of the pollen and 
embryo-sac mother-cells. Bot. Gaz. 35: 250-282. 1903. 
(07). The development of the heterotypic chromosomes in 
pollen mother-cells. Ann. Bot. 21: 309-347. 1907. 
(09). Prophases of heterotypic mitosis in the embryo-sac 
mother-cell of Lilium. Ann. Bot. 23: 343-352. 1909. . 
Explanation of plates 23 and 24 
All figures were drawn trom enn with the aid of the Abbé camera lucida and 
with Leitz 1/12 immersion and ocular IV or age Zeiss apochromatic immersion 
mm., apert. 140, and seiautn g ocular 12. gnification of figures 3, 4; 9» 
10, II, I2, 14, 18 and 19 about 2000; all other Plt about 1600 
IG. I. Young pollen mother-cell soon after the last somatic divieion 
Fic. 2. Pollen mother-cell near the close of the period of — ay: ie nucleus 
is almost as large as it ever becom 
hin section of a ea passing into synapsis; the net-work is form- 
inga ‘hiresa or spirem. 
Fic. 4.. A similar stage, showing nearly the whole nucleus. These two figures 
were near each other in the same “leas 
FIG. 5. yl is complet 
Fic. 6: The cen mass ae up. The very long, slender thread has 
shortened into a eee 
Fic. 7 e thick, pies spirem. 
Fic. 8. The same stage as Fic. 7. A longitudinal split is seen in two or three 
Fic. 9. The spirem as it frequently appears before the rearrangement into the 
second contraction. At this stage the spirem may appear lumpy or with thicker 
and thinner portio 
FIG. 10, II. ial steps of the rearrangement. The chromatin cord is, as 4 
rule, much more entangled than in these figures. Indications of transverse segmen- 
tation are seen in FIG. Io. 
Fic. Segmentation is about oouulessd, The two members of each bivalent 
are ROS ‘eben each ot 
Fic. 13. Similar to es preceding; the twisting is more pronounced in all 
chromosomes. 
Fic. 14. Chromosomes beginning to untwist preparatory to the formation of 
the spindle. 
