1912] STEVENS—HETEROSTYLOUS PLANTS 305 
Houstonia caerulea 
The nuclei and chromosomes of the pollen mother cells are so 
small that many of the prophasic phenomena could not be observed 
with accuracy, but the formation of the gemini and the reduction 
division seem to follow the “‘hétérohoméotypique scheme.” 
Some portions of the nuclei go poate the postsynaptic changes 
in advance of others. 
Diakinesis is characterized by a portion of the gemini arranging 
themselves end to end in a sort of chain. 
The reduced chromosome number is 16. 
During interkinesis the chromosomes apparently remain 
unchanged, and are arranged about the periphery of the nucleus. 
The nucleoli which appear at this stage resemble the chromosomes 
when stained with haematoxylin. 
No difference is apparent in the chromosomes which separate 
in the heterotypic division. 
In the anaphase of the reduction division the chromosomes of 
the short-styled form are slightly larger than those of the long- 
styled form. 
The separation of the cells of the tetrad occurs in the same way 
as in the buckwheat. 
YALE UNIVERSITY 
New Haven, Conn. 
LITERATURE CITED 
1. ALLEN, CHarLEs E., Nuclear division in the pollen mother cells of Lilium 
canadense. Ann. Roteny 19:190-258. 1905. 
. Bateson, W., and Grecory, R. F., On the inheritance of heterostylism 
in Primula. Proc. Roy. Soc. Leadon 76: 581-586. 1905. 
3- BLAKESLEE, A. F., The nature significance of — differentiation 
in plants. Seimine 25: 366-372. 
4. Correns, C., Die Bestimmung “ Vaud des Geschlechts. Leipzig. 
Nv 
1907. 
5. Dartinc, C. A., Sex in dioecious plants. Bull. Torr. Bot. Club 36:177- 
1QQ. 1909. 
- Darwin, CHARLES, On the two forms or dimorphic condition in the species 
of Primula, and on their remarkable sexual relations. Jour. Proc. Linn. 
Soc. 6:77. 1862 
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