494 Digby . — Observations on ‘ Chromatin Bodies ' and their 
When the nuclei have completed their synaptic rearrangement, and the 
‘ bodies ’ have been extruded and are lying in the neighbour cells, more or 
less abutting against the wall dividing the parent cell from the invaded cell 
(PL XXXIII, Fig. 9), the knot begins to loosen and the cells to separate. 
It is not uncommon in Galtonia to find at this time that the whole synaptic 
knot breaks up into ‘ chromatic bodies This invariably indicates that the 
nucleus, instead of passing into the subsequent spireme stage, disintegrates 
and dies. Often two loculi, or even all four, may have their pollen mother- 
cells in this aborted condition. 
Walls of the Pollen Mother-cells. 
It is necessary here to sketch the history of the walls of the pollen 
mother-cells, which come into such close relationship with the ‘ chromatic 
bodies ’. During the stages leading to synapsis, the cells are polyhedral in 
shape, and form a closely fitting and compact mass (PI. XXXIII, Fig. 9). 
The cell-walls are thin and evidently are composed both of pectose and of 
cellulose, as they stain brightly with Methylene Blue and with Ruthenium 
Red (pectic stains), and even more brilliantly with Congo Red (cellulose stain). 
They consist of a clear middle lamella, which stains homogeneously, and 
in which occasionally granules, apparently cytoplasmic, may be found ; this 
layer is bounded on either side by fine membranes. The cytoplasm of the 
cells extends to the walls. When the cells are preparing to separate the 
middle lamella swells considerably but unevenly (PI. XXXIV, Fig. 11): 
in some places it may be considerably thickened, whilst in others it remains 
thin ; at the same time it loses its staining capacity and appears as 
a colourless space. 
Some chemical change is apparently proceeding in the interior of the 
wall, that is to say in the colourless layer, which causes the swelling, and 
forces the delicate membranes severally to round off and limit the cytoplasm 
of the cell with which they are in contact. In Fnnkia Sieboldiana a thin 
membrane, a specialized part of the middle lamella, has been seen in the 
clear space of the wall, but in Galtonia this is not visible. Protoplasmic 
connexions across the walls are most obvious (PI. XXXIV, Fig. 14). Thus 
each pollen mother-cell is enclosed in its own wall (PI. XXXIV, Fig. 17). 
The cytoplasm gradually contracts, so that by the time that the nucleus 
contains definite chromosomes there is a wide space between the circular 
enveloping wall and the enclosed, somewhat irregularly outlined cytoplasm 
(PI. XXXIV, Fig. 18). The wall has by this time resumed its staining 
reaction, and appears as a thin membrane, often with many adhesions and 
granules on its surface. The wall persists, with slight modifications in its 
structure, throughout the first and second meiotic divisions, and is only 
finally broken down when the pollen grains are set free in the cavity of the 
pollen-sac. 
