The development and behavior of the chromosomes in the first 
or heterotypic mitosis of the pollen mother-cells of 
Allium cernuum Roth 
Davip M. MotTtTiER AND MILDRED NOTHNAGEL 
(WITH PLATES 23 AND 24) 
It may seem to the reader of cytological literature that 
whoever offers a contribution upon Allium might well preface 
his remarks with an apology for so doing. However, certain 
favorable forms of both plants and animals will doubtless ever 
remain objects of investigation. On looking about for favorable 
material for class use, the senior author came upon a species of 
wild onion, common in certain localities in Indiana, namely, 
Allium cernuum Roth, a species which is regarded as more favorable 
than the much used Allium Cepa. 
A study of mitotic phenomena has been made in both vege- 
tative and microspore mother-cells, and the results obtained and 
conclusions reached differ so much in certain respects from those 
of Bonnevie (’11), as set forth in a recent contribution on Allium 
Cepa, that we have decided to present the results of our observa- 
tions on the pollen mother-cells at this time, reserving an account 
of the process of nuclear behavior in vegetative cells for a future 
publication. 
In describing the resting stage of the nucleus in the pollen 
mother-cell of Allium Cepa, Bonnevie (’11, 197) asserts that a 
number of threads radiate from a chromatin knot or lump (Chro- 
matinknoten), being continued into the meshes of the nuclear net. 
“Yom Chromatinknoten sieht man eine Anzahl Fadchen, die in 
den Maschen des Kernnetzes ihre Fortsetzung finden, radiar 
ausstrahlen.” With the disappearance of the anastomoses 
between these radiating threads, the latter gradually became more 
distinct throughout their entire length, at the same time appearing 
always zigzag or spirally twisted. Precisely the same structure is 
reported for the resting nucleus of somatic cells. Following this 
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