544 
R. RUG(iRES (iATES AND NESTA 'J’HOMAS. 
pollen mother-cells contain very little cytoplasm. Often the 
cell-walls between tlie mother-cells of an anther are very 
imperfectly formed or almost wholly lacking, so that their 
protoplasm forms a continuous mass from one end of the 
anther to the other (fig. 32). The nuclei in these cases have 
usually disappeared. In such anthers the degeneration must 
have begun in the archesporial tissue. In other cases 
(figs. 33, 34) the cell wmlls between mother-cells are 
nearly complete, but nuclear matei-ial passes through 
openings in the walls into the adjacent mother-cells. This 
may happen when the nuclear contents are fused into a 
single mass (fig. 33), or when they are in discrete chromo- 
somes (fig. 34). In the latter case the chromosomes are 
smaller than normal and frequently scattered in the cyto- 
plasm. A condition somewhat similar to that shown in 
fig. 33 was described by Gates (19IIa, fig. 9) in . mut. 
gigas. In the hitter case, however, the tapetum was 
developed, though the mother-cells afterwards remained in 
contact wdth it. The nuclei Avere in synapsis, and shoAved no 
signs of abnormality except in the extrusion of chromatin 
into adjoining cells. Similar conditions Avere described by 
Miss Digby (1909) in Galtonia. 
Fig. 35 represents a pollen mother-cell of CE. lata rubri- 
calyx in another condition of degeneration. The cytoplasm 
becomes highly vacuolate and scanty, Avhile the nucleus 
disappears, leaAung only pale-staining scattered chromatin 
i-emnants. This condition is a fairly common one. 
In addition to these peculiarities, cases of extra nuclei in 
the pollen tetrads are common. The extra nuclei are, of 
course, formed by chromosomes left behind in the cyto- 
plasm, as Avas shoAvn in CE. mut. rubrinervis (Gates, 
1908a), CE. mut. gigas (Gates, 1911a), and other forms, 
where they occui*, though less commonly. It is not necessary 
to figure them again here. Such cells probably all degene- 
rate, except perhaps in rare instances. 
