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Explanation of plates XXIX and XXX. 
The fignres were drawn with the aid of a Bausch and Lomb camera lucida. 
The lenses used were a Zeiss apochromat objective 2 mm ap. 1.30 with a Zeiss 
compensating ocular 18. The figures are reduced one fourth in reproduction, 
giving a magnification of nearly 3000 diameters. This affords a direct com- 
parison of the size of the pollen mother cells in O. gigas with those in my 
paper on O. ricbrinervis, (Gates 1908b). 
Fig. 1. Side view of heterotypic spindle in pollen mother cell in meta- 
phase. The chromosomes are loosely scattered in the middle region of the 
spindle, mostly nnpaired. Twenty-three are in view. 
Fig. 2. A rather exceptional case, in which the chromosomes are arranged 
in two fairly regulär parallel series which have begun to pass toward the poles. 
Fig. 3. Twenty-eight chromosomes present. Two chromosomes paired, 
each showing a longitudinal split for the next mitosis. Pale-staining nucleolus 
at side of spindle. 
Fig. 4. Heterotypic spindle in polar view. The twenty-four chromosomes 
represented were scattered for a considerable distance along the long axis ot 
the spindle. 
