Mother-cells of Smilacina racemosa (L.), Desf. 479 
species, and attach no special significance to this difference in size, as some 
cytologists do. The sizes do not remain constant throughout any one 
species ; so no hereditary significance can be attached to these differences. 
In Smilacina racemosa different sizes of chromosomes appear in the seg¬ 
mented stage and on the spindle plate, but the differences in size and shape 
are not constant: that is, a chromosome of certain size or shape cannot be 
found in all nuclei at this stage, and the chromosomes are constantlyxhanging 
size as they contract. 
Lawson (’ll a) gives 20 as the probable haploid number of chromosomes 
in the Smilacina with which he worked, but later (Lawson T2) changed the 
number to 14. McAllister (T 3 ) gave 24 for the haploid number in Smilacina 
racemosa. The findings in this investigation agree more nearly with 
McAllister, the countings showing from 20 to 24 chromosomes. 
The cell-walls are thin in the resting stage, but, as the cells round off 
during and immediately after the synaptic stage, they begin to thicken, and 
in the segmented and spindle stages a very thick special wall surrounds the 
pollen mother-cells. (Compare Figs. 1, 7, 14, 15, 20, and 21.) 
Spindle. The chromatin thread undergoes a continuous shortening 
and thickening throughout the prophases, and, when the chromosomes 
appear on the spindle in the metaphase, they are very short and thick 
(Fig. 21). There is no indication, in the nuclei examined in this investiga¬ 
tion, that the spindle fibres are formed by a gradual contraction of the 
nuclear membrane, a closing in around each chromosome and a subsequent 
tension resulting in the cytoplasm forming fibres, as advocated by Lawson 
(’ll B) for the microspore mother-cells of Disporumgladiolus, Yucca , Hedera , 
for the vegetative cells in the root-tip of Allium , and later for the microspore 
mother-cells of Smilacina. The difficulties involved in such a process have 
been discussed by Farmer (T2 and M 3 ), and further discussion seems useless 
here. In no case was the nuclear membrane in Smilacina racemosa seen to 
contract around the chromosomes in such a manner as Lawson described. 
The spindle fibres, rather, appear to be formed in the manner described by 
Mottier (’ 97 ) and others. It was often found that in the same loculus were 
nuclei in the typical segmented stage and other nuclei with fully developed 
bipolar spindles. In some nuclei the nuclear membrane appeared to be 
partly broken down, in some fibres were appearing, in others portions of the 
membrane persisted as fibres appeared, while in still others the membrane 
was entirely broken down and the chromosomes were arranged on the 
spindle in the typical metaphase condition. 
Summary. 
1. The microspore mother-cells of Smilacina racemosa have the nuclear 
contents in a finely divided state during the resting stage, with irregularly 
shaped granules held in the meshes of a fine linin network. 
