Nuclear Division in the Hepciticae. 5 1 1 
In the liverworts examined by me, the nucleolus was associated 
with the chromosomes In an unmistakable and remarkable 
manner. In other plants (e. g. Lilies), on the contrary, this 
relation may be merely subordinate in character, whilst large 
portions of the fragmented nucleolus are cast out into the 
cytoplasm. This occurs in Lilium Martagon , and according 
to Zimmermann 1 it holds good also for a large number of 
diverse plants. Zimmermann’ s observations have been chal- 
lenged by Humphrey 2 , but I can safely state that in the 
account which Zimmermann gives of the process In Lilium 
Martagon he is certainly correct, and that the appearances 
shown in his figures may be seen in almost any well-preserved 
material which has been appropriately stained. There is also 
evidence to show that the nucleolus may behave differently in 
different tissues of even the same plant. Thus Guignard 3 
found that in the archesporial cell-divisions of Psilotum , 
when the chromosomes have congregated in the equatorial 
plate, the nucleoli, which have diminished somewhat in size, 
are cast out into the surrounding cytoplasm. But in the 
.spore-mother-cells of the same plant the nucleoli are almost 
entirely dissolved within the nucleus, and at most only a few 
relatively small particles are cast out and continue to be 
recognizable in the cytoplasm. This latter observation seems 
at first sight hardly to harmonize with the course pursued by 
the same body in Lilium , but it must be remembered that in 
the latter plant the nucleolus reaches an enormous size, and 
that it does, as a matter of fact, lose a good deal of its sub- 
stance (as is proved by the extensive vacuolation) before its 
remains are extruded into the extra-nuclear protoplasm. 
In a considerable number of cases, the decrease of nucleolar 
substance is contemporaneous with the growth of the chromo- 
somes, and I cannot regard this coincidence as a merely 
accidental one. I have been led to this view, not only by the 
study of the earlier phases of karyokinesis, but also by a con- 
1 Zimmermann, Beitr. z. Morph, u. Physiol, d. Pflanzenzelle, Bd. II, Heft i. 
2 Nucleolen u. Centrosomen. Ber. d. deutsch. Bot. Gesellsch. , 1894. 
3 Guignard, Sur l’origine des spheres directrices. Journ. d. Bot., 1894. 
N n 2 
