66 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
splitting begins in later synapsis, reaches its maximum with loop- 
formation, and then becomes less distinct, until in diakinesis it is 
scarcely visible. In the early stages the chromosomes are united end to 
end to form a continuous thread. In the second synapsis the thread 
folds together, assumes a spiral form and then segments into separate 
Fig. 3. 
Fig. 4. 
pairs of chromosomes. C. coroncirium thus exhibits an intermediate type 
of reduction-division which should reconcile the “ folding ” and 
“ splitting ” theories. 
Chrysanthemum exhibits an unusual type of wall-formation in the 
tetrad-division of the pollen-mother-cells. The cell-wall has four 
Fig. 5. 
ingrowths which gradually grow inwards and meet together, dividing 
the cell into four daughter-cells. “ Shasta-Daisy ” is a bastard resulting 
from the crossing of a Japanese species of Chrysanthemum with another 
species — probably C. arcticum. Its nuclear-division is peculiar and 
indistinct ; in the heterotypic stage 85 chromosomes are visible, but 
their subsequent behaviour shows that 40 of these are monovalent and 
