INTRODUCTION. 



ing shorter and thicker, and frequently no trace of the longitudinal 

 splitting can be recognized. There is thus formed the loose, hollow 



FIG. 6. Prophase and early stages in development of spindle inj heterotypic mitosis of pollen mother 

 cell. A, B, Lilium can did urn. C, D, L. martagon. 



A, the kinoplasmic spindle fibers arranged radially about the nucleus, large nucleolus present, and th< 



chromosomes, each consisting of two rather thick segments twisted about each other, lie along th< 

 nuclear membrane or scattered through nuclear cavity. 



B, same developmental stage as A ; here the kinoplasmic fibers are disposed partly radially and partlj 



in form of a weft lying in cytoplasm midway between nucleus and cell-wall. 



C, the spindle fibers are encroaching upon the nucleus, forming a weft about it ; the nuclear membram 



as such has nearly disappeared ; it seems to have been converted into fibers. 



D, multipolar spindle complex, in which the chromosomes are irregularly distributed. 



spirem, which segments by transverse division into the chromo 

 somes. 



