40 
Wager . — The Nucleolus and Nuclear Division 
Wiegand 1 points out that the nuclei in Potamogeton are all very pecu- 
liar, differing from the ordinary type in having the chromatin mostly 
aggregated in a ball at the centre of the cavity, instead of being distributed 
on the linin-network. 
Andrews 2 shows that in the nuclei of Magnolia and Liriodendron the 
nucleolus is large, stains deeply, and has a conspicuous vacuole. The linin- 
network is chiefly connected with the nucleolus. The threads of the net- 
work are at first smooth and uniform in diameter. At a later stage 
granular masses of chromatin appear on it, which gradually increase in size 
and become the chromosomes. The nucleolus at about the same time 
disappears entirely. c It is probably utilized as food in the growth of the 
chromatin masses, for they stain much more readily at this time than at an 
earlier stage.’ The chromosomes therefore arise from the resting nucleus 
as irregular masses without a previous formation of the usual spire m, and 
their identity from the first to the second mitosis is not maintained. 
Blanche Gardner 3 , on the root-cells of Vicia Faba, comes to the con- 
clusion that the chromosomes derive ‘ at least a large part of their material 
from the nucleolus.’ ‘ The nucleolus is related to the nuclear reticulum in 
such a way that the fibres penetrate its substance.’ Previous to the nuclear 
division the nucleolus divides into two. Then the thin, long, almost con- 
tinuous nuclear thread can be seen ‘ at one or at several points ’ to ‘ dip into 
the nucleolus.’ ‘ The nucleolus now begins to transfer its contents into the 
nuclear thread.’ The thread becomes thicker and stains just like the 
nucleolus, which gradually disappears. This spirem thread then divides 
transversely into the chromosomes. In the daughter-nuclei the chromo- 
somes ‘ aggregate to form a small, dense, blue-black coil.’ Out of this mass 
the nucleolus is formed. The chromosome-coil gives up its chromatin 
and gradually loses its dark colour. ‘ At first these chromosomes are full of 
the dark chromatin-granules ; these become fewer and fewer as the nucleolus 
becomes larger and more distinct V 3 
Methods. 
The root-apices of varieties of the common French Bean, Phaseolus 
vulgaris , L., were used. Sections were cut both by hand and by the micro- 
tome. Various fixing-fluids were used, but Perenyi’s fixing-fluid was the 
most useful. Among the many staining methods tried, Heidenhain’s iron 
1 Wiegand, Karl M., The Development of the Embryo-sac in some Monocotyledonous Plants, 
Bot. Gaz., xxx, 1900. 
2 Karyokinesis in Magnolia and Liriodendron with special reference to the Behaviour of the 
Chromosomes, Bot. Cent., xi, 1901, Beih., p. 134. 
3 Studies on Growth and Cell-division in the Root of Vicia Faba . Contributions from the 
Botanical Laboratory, University of Pennsylvania, ii, 1901. ' 
4 Chamberlain, in a recent paper (Bot. Gaz., xxxvi, 1903, p. 28) concludes that in Pellia the 
nucleolus contributes material to the chromosomes and spindle. 
