580 
Saxton. — Contributions to the 
fix and embed satisfactorily. On the other hand, the nuclei are somewhat 
small (though slightly larger than in the Callitroi'deae) ; and the large 
amount of starch present in the later stages of the meiotic divisions is apt 
sometimes to obscure the cytological details. 
The resting nucleus (PL XLIV, Fig. i) appears practically identical in 
structure with that figured by various investigators in other pollen mother- 
cells. There is a network of anastomosing linin threads with numerous rather 
conspicuous chromatin granules, and a large nucleolus which can usually be 
seen in optical section to be hollow. No starch is visible. As the nucleus 
prepares for synapsis, the linin thread thickens to form a deeply staining 
slender spireme (Fig. 2). This spireme is not one single coiled continuous 
thread without anastomoses, but can be clearly seen to branch at certain 
points. Isolated starch grains now appear in the cytoplasm. Then the 
mesh begins to contract to one side of the nuclear cavity (Fig. 3), this being 
quickly followed by complete synapsis (Fig. 4). In Tetraclinis , as these 
figures demonstrate, there is no approach whatever to the condition claimed 
by Lawson ( 28 ) to be characteristic of synapsis. According to that author 
synapsis consists in an expansion of the nuclear cavity, and not in a con- 
traction of the contents, but even his own figures, as mentioned in a criticism 
by Professor Farmer, do not support his contention. It may be mentioned, 
however, that an enlargement of the whole nucleus does occur in Tetraclinis 
about the time of recovery from synapsis. 
As far as can be estimated the nuclei remain for some time in this con- 
tracted condition, practically no structure being visible. As recovery begins 
to set in, loops may sometimes be seen projecting from the periphery of the 
contracted mass (Fig. 5). Very soon recovery is complete, a very slender 
spireme being formed (Fig. 6), in which fewer anastomoses can be seen than 
before contraction. This spireme gradually thickens and shortens (Fig. 7), 
and at the same time the number of anastomoses becomes less, though it 
does not appear as though the thread ever becomes entirely free from 
branching. Up to this time no trace whatever has been seen of any 
splitting of the thread, such as occurs regularly in some angiospermous 
pollen mother-cells at this time. Traces of the same splitting have been 
claimed by Lewis ( 29 ) in Pinus and Thuja , and by Miss Ferguson in Pinus. 
The stage following (Fig. 8) is that sometimes called the second con- 
traction figure (Farmer and Moore ( 16 ), Mottier ( 33 )), but in Tetraclinis no 
real contraction occurs so far as can be seen. This figure is of interest 
as showing the only phenomenon which could be interpreted as splitting 
of the thread, though such an appearance is probably due merely to the 
approximation of the two sides of a loop. 
Next the thread breaks up to form about a dozen bivalent chromosomes, 
and these soon shorten and thicken to form the curved bodies seen in Fig. 9. 
The earliest stages of spindle formation have not been seen distinctly in 
