Dixon — On the Chromosomes of Lilium longiflorum. 719 



probable. They are of various sizes, and are budded off from the 

 originating nucleus in a manner resembling the budding of yeast cells. 

 Fig. 18 shows one of these nuclei being formed from the large central 

 nucleus. It may be noticed that this form of direct division is not 

 uncommonly to be seen in the nuclei of the endosperm of Fritillaria 

 imperialis, and is very unlike in appearance the typical direct division 

 found in Tradescantia and Characeae, «S:c., where the resulting nuclei 

 into which the original nucleus divides are about the same size. 

 Protoplasmic strise radiate from the products of this direct fission, 

 just as they do fi'om nuclei formed by mitosis, into the surrounding 

 protoplasm. 



explajSTation or plate xxiii. 



Figs. 1-12, Lilium longiflorum,. 



Fig. 1 . — Diaster in the 5th cell from the surface of the apex, appear- 

 ing in two successive longitudinal sections of a bud. 



Fig. 2. — Pollen mother-cell. Nuclear thread is seen doubled in places. 

 X 500. 



Fig. 3. — Pollen mother-cell, after the differentiation of the chromo- 

 somes. X 500. 



Fig. 4. — Same as Fig. 3 ; later stage. 



Fig. 5. — Diagram illustrating the forms assumed by the chromosomes 



of the pollen mother- cells prior to their arrangement in the 



nuclear plate, x 1000. 



Fig. 6. — Pollen mother- cell, nuclear plate seen from the equatorial 

 plane. The horizontal division of one chromosome is nearly 

 complete, which is also indistinctly divided vertically, 

 x 500. 



Fig. 7. — ]S"uclear plate of pollen mother-cell seen from one of the 

 poles. The short thick chromosomes appear more or less 

 distinctly composed of two approximated portions. Fibres 

 of the achromatic spindle are seen between some of the 

 chromosomes, x 500. 



Fig. 8. — Nuclear plate in pollen mother-cell seen from the equatorial 

 plane. The chromosome on the right is dividing horizon- 

 tally into two V-shaped daughter chromosoiucs. x 500. 



K.I. A. PROC, SEH. III., VOL. III. 3 B 



