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The Cytology of Zygnema ericetorum. 
The chloroplast. In the living cell the chloroplast is very 
indefinite, and it is scarcely possible to make out its limitations 
except by the use of appropriate fixing and staining reagents. Very 
frequently, particularly in material collected in the autumn, the 
chloroplast is more or less completely obscured by oil-globules. 
The characters of the chloroplast were most clearly brought out by 
fixing with corrosive sublimate, then washing in water for twenty- 
four hours and staining. The most successful stains were Delafield’s 
haematoxylin and fuchsin-iodine-green. The latter was used at a 
strength of 1 vol. of a concentrated aqueous solution of fuchsin to 
12 vols. of a 1 per cent, iodine-green solution. The filaments were 
allowed to stay in this mixture for twenty minutes, then washed in 
water for a few minutes, taken up through various strengths of 
alcohol to 95 per cent, alcohol, then transferred to a mixture 
composed of 100 c.c. of 96 per cent, alcohol, 1 c.c. of glacial acetic 
FiO. 1. Two examples of the aquatic form of Zygnema ericetorum from N. 
Wales. Fixed with corrosive sublimate and stained with fuchsin-iodine- 
green. x 1750, 
