276 Wisconsin Academy of Sciences, Arts, and Letters. 
reported (Overton, ’096, ’ll). In order to be certain that the 
figures and conclusions drawn from them are correct, the prepar¬ 
ations from which the drawings were made and many other slides 
have been many times re-examined during the last ten or twelve 
years, especially in the light of the interpretations above referred 
to. In the present account the aim will be to give a careful de¬ 
scription of the somatic chromosomes during the reconstruction 
stages, to follow in detail their structure and arrangement in the 
resting nucleus, and to determine how they are again reformed 
preparatory to division. 
Materials and Methods 
The material was collected in early Spring before the roots had 
attained great length by removing entire plants from the humus 
in which they grew. The soil was carefully removed, and the 
root tips were severed and dropped at once in the various fixing 
fluids. In order to compare the effects of different fixing fluids 
upon the nuclear and cytoplasmic structures, a large number of 
fixatives were used, chiefly Flemming’s chromic-acetic mixtures in 
various strengths and modifications, Carnoy’s alcohol-acetic and 
alcohol-acetic-chloroform mixtures, Hermann’s platinic chloride- 
acetic-osmie mixture, Merkel’s chromic-platinic chloride mixture, 
Juel’s zinc chloride-acetic-alcohol mixture, Guignard’s chromic- 
iron chloride-acetic mixture, Kaiser’s sublimate-acetic mixture, 
picric-acid, mixtures, Worcester’s formalin-sublimate-acetic mix¬ 
ture, Gilson’s sublimate-nitric-acetic mixture, and Zenker’s subli¬ 
mate-potassium bichromate-acetic mixture, with Tellyesniczky’s 
modification. Fairly good results were obtained with Flemming’s 
stronger osmic fluid. As this is the mixture most generally used 
for cytological work in botany, I have compared its fixation very 
carefully with that obtained by the other fluids and find that it 
apparently often causes artifacts, which will be discussed in the 
description of my observations. Merkel’s fluid gave by far the 
best results, preserving the nuclei and cytoplasmic structures 
equally well, and preparations fixed in this fluid were found to 
be far superior to all others. The results described in this paper 
are, therefore, based mainly upon preparations fixed in this fluid. 
Comparisons were always made, however, with osmic fixation, 
which apparently shrinks the nuclear structures and may thus 
easily lead to misinterpretation. Throughout this paper Merkel’s 
fixation is considered the normal one. 
