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METHODS IN PLANT HISTOLOGY 
fixing agent, but in later stages, such as are shown in Figure 113, strips 
should be cut off from the sides of the ovary in order to secure more 
rapid fixing and more perfect infiltration with paraffin. The dotted 
lines in Figure 111C, show about how much should be cut off. This 
is a much better plan than to secure rapid fixing and infiltration by 
cutting the ovary into short pieces, because the ovules will be in 
Fig. 108 .—Lilium canadense: photomicrograph of part of transverse section of ovary, 
showing longitudinal section of ovule with megaspore mother-cell, just before the formation of 
integuments. Fixed in chromo-acetic acid and stained in iron-alum haematoxylin. Eastman 
Commercial Ortho film, Wratten H filter (blue); Spencer 4-mm. objective, N.A. .66; ocular X6; 
arc light; exposure, 2 seconds. Negative by Dr. P. J. Sedgwick. X400. 
about the same stage cf development throughout the ovary, and when 
one finds desirable stages like those from which these photomicro¬ 
graphs were taken, it is gratifying to have these pieces as long as 
possible. 
Chromo-acetic acid, with the addition of a little osmic acid, 
is good for fixing the entire series. Iron-haematoxylin, with a 
light touch of orange, is best for the chromatin. For general beauty 
