The individuality of the chromosomes and their serial 
arrangement in Carex aquatilis. 
By 
Arlow Burdette Stout. 
AVith plates XI and XII. 
Much evideiice has accumulated in recent years in Support of the 
doctrine of the individuality of the chromosomes. Their permanence, 
division, and growth are now well established facts. Observations are 
also recorded as to the relations of these individual units both in the 
general Organization of the nucleus and in regard to the possible pairing 
of the maternal and paternal chromosomes in the somatic nuclei. Such 
investigations are of special significance for the problems of heredity. 
The studies here reported concerning the nuclear phenomena in Carex 
aquatilis relate especially to the identity of the individual chromosomes 
in all stagcs of nuclear development and to the fixed relative place ar- 
rangement of these individual units. 
JuEL (1900) describes and figures the principal stages of pollen 
formation for Carex acuta and his work is all that we have on the cyto- 
logy of the genus Carex. His figures show stages from synapsis to the 
development of the generative cell and prove conclusively that three of 
the microspore nuclei degenerate, thus confirming and extending the 
work of Elfving (1879) and Strasburger (1884) on Heleocharis. Juel 
does not determine the method of chromosome reduction in the hetero- 
typic division. The chromosomes do not even appear visibly paired in 
his figures of diakinesis. Still the general appearance of his figures for 
Carex acuta is strikingly similar to that of the same stages as I find them 
in Carex aquatilis. 
My material was collected in the vicinity of Madison, Wisconsin, 
where Carex aquatilis is abundant. Tips from the large soll roots were 
