The mechanics of mitosis in the pollen-tube of Tulipa

Abstract

The division of the generative nucleus in the pollen-tube of the higher plants has been studied by several authors, with results differing widely from one another even when concerned with the same genus. For example, Koernicke (1906), Welsford (1914), and O’Mara (1933) have investigated various species of Lilium . Koernicke and Welsford describe the formation of a definite though narrow metaphase plate, while O’Mara, in spite of his illustration (fig. 9), is of the opinion that there is no such regular congression owing to the narrowness of the tube. Trankowsky (1930) finds a metaphase plate in Hemerocallis , the pollen-tube of which is wide in comparison with the size of the spindle, but not in Galanthus or Convallaria . Wulff’s (1933) observations are weakened by his confusing anaphase with pro-metaphase, and centric with nucleolar constrictions. A further point at issue is whether the generative cell divides by constriction or by the formation of a cell-plate, the more usual method in the higher plants. Koernicke illustrates a well marked cell-plate, but Wulff and others are of the opinion that division is by constriction.