The Behaviour of the Chromosomes in Pinus 
and Thuja. 
BY 
I. M. LEWIS, 
University of Indiana . 
With Plates XXIX and XXX. 
^THOUGH the behaviour of the chromosomes in the two divisions 
attending spore formation in the higher seed plants has been a 
favourite subject for research, the majority of investigators have confined 
their attention to certain favourable forms of the Angiosperms, and only 
a few extensive investigations have been made in the Gymnosperm group. 
Among these, the work of Miss Ferguson (’04) for Pinus is doubtless the 
most comprehensive. The results obtained by that writer differ so much 
from conditions that are known to exist in other forms that their confirma- 
tion seems much to be desired. Certain other questions have arisen since 
the time at which the genus Phius was investigated which render desirable 
a study of some members of this group. Among these questions may be 
mentioned the manner of conjugation of the maternal and paternal chromo- 
somes to form the bivalents and the possibility of recognizing prochromo- 
somes in the resting nucleus. 
The forms investigated were Pinus sir obits , P. austriaca , P. Laricio , 
and Thuja occidentalis. Figures are shown from the different species, but 
when differences exist such differences have been noted. Frequent refer- 
ences are made to the work of Miss Ferguson (’04) which is, in a large 
measure, confirmed by my own results. 
Methods. 
The methods used were such as are employed in any piece of modern 
plant cytology. The cones were fixed as soon after their removal from the 
tree as was possible. The fixing fluid used was the chrom-osmic-acetic 
fluid of the formula proposed by Mottier (’97). The staminate cones were 
cut into small pieces, and the hard points shaved off with a razor, thus 
rendering the sectioning of the pieces more satisfactory. In some cases the 
individual sporophylls were removed and fixed. This causes considerable 
difficulty in sectioning, but the fixation in material so treated was found to 
[Annals of Botany, Vol. XXII. No. LXXXVIII. October, 1908.] 
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