﻿Pollen development and degeneration in Zebrina pendula, with 

 special reference to the chromosomes 



Robert T. Hance 



The following work on the cultivated wandering Jew, Zebrina 

 pendula Schniz., a plant which does not set seeds, was begun with 

 the intention of studying any differences which might exist 

 between the germinal and somatic chromosomes. So many 

 interesting variations in the development of the pollen were 

 found that the present paper is confined almost entirely to a 

 description of these peculiarities. 



The chief points developed in the following article are: 



1. Parasynapsis occurs, which may readily be followed through 

 the heterotypic divisions. 



2. There is no fusion of chromosomes in the heterotypic 

 division. The chromosomes appear in distinctly separated pairs. 

 There are presumably one half as many pairs as there are somatic 

 chromosomes and each pair behaves as a single chromosome — 

 splitting transversely at division. Each daughter cell, therefore, 

 receives as many pairs as the mother cell possessed though d 

 one half the size. 



3. The number of pairs varies from twelve to fifteen. 



4. Chromosomes having the appearance, at first sight, of 

 heterochromosomes appear, but further study shows that any 

 chromosome may behave as such. 



5. Entire chromosomes and fragments of chromosomes may 

 be omitted from the reformed nucleus in either the heterotypic 

 or homotypic divisions. 



6. The pollen grains grow to a large size, the nucleus may or 

 may not divide, and the cell then vacuolates and goes to pieces 

 leaving only the outer coat shriveled and cracked. 



7. Such somatic mitoses that have been observed show a long 

 slender chromosome, whereas the germinal cells possess a short 



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