224 Sargant • — Sexual Nuclei in L ilium Martagon. 
Fig. 27. Four chromosomes on spindle. The segments of each are in the act 
of separating, x 1000. 
Fig. 28. Section of pollen-grain in which the daughter-chromosomes of the 
dividing nucleus are just separating. At the inner pole is a differentiated mass 
of cytoplasm . x 5 8 5 . 
Figs. 29-34. Karyokinesis of generative nucleus in pollen-tube. 
Fig. 29. Stigma slightly enlarged. 
Fig. 30. Section of pollen-grain in situ on stigma and just about to put out 
tube : v. n. vegetative nucleus ; g. n. generative nucleus already in spirem-stage. 
x 585- 
Fig. 30 a. Empty shell of pollen-grain with remains of tube, from dissection 
of stigma, x 100. 
Fig. 31. Stigmatic hairs with pollen-grains germinating among them: p.t. 
tube from which exine (ex) has fallen off, and containing generative nucleus (g. n .) ; 
p.g. pollen-grain which has put out coiled tube. x66. 
Fig. 32. Pollen-tube containing generative cell in which generative nucleus is 
on the eve of forming chromosomes from lengths of spirem-ribbon. x 1000. 
Fig. 33. Pollen-tube in which generative nucleus has formed twelve chromo- 
somes, each divided longitudinally, x 1000. 
Fig. 34. Germinating pollen-grain from dissection. Three nuclei, x 290. 
DIAGRAMS. 
The two series of diagrams illustrate the difference between the heterotype 
process of nuclear division in Lilium Martagon and the homotype process. 
The homotype series is founded on drawings of the vegetative nuclei which 
are seen in tissues of the young ovule and ovary (I, p. 451). They are drawn 
as though each nucleus had twelve chromosomes in place of twenty-four. 
The heterotype series is founded on drawings from the first division of the 
embryo-sac nucleus. The spindle is drawn on the same scale as the homotype 
spindle, which makes the heterotype chromosomes appear smaller than the 
homotype chromosomes. For the ratio of spindle-length to chromosome-length is 
greater in the heterotype than in the homotype karyokinesis. 
