and Laboratory Methods. 1703 



Wash in fifty per cent, alcohol. The first named fixing agent, however, allows 

 a sharper staining of the nuclear figures. 



Fuchsin, safranin and gentian violet do not stain well ; methyl green, iodine 

 green and methyl blue are better. The following method gave the best results : 



Crystals of ammonia alum - - - - 75 parts. 

 Water .-...-. 750 parts. 



Dissolve the crystals in the water and add 



Glycerine - - 125 parts. 



Alcohol (94 per cent.) - - - - - 100 parts. 

 Saturated alcoholic solution of haematoxylin 25 parts. 



The solution must stand for several weeks in a beaker, covered only by a 

 piece of filter paper, before it is ready for use. Then stain for twenty-four hours 

 in a mixture of 10 parts of the above solution in 100 parts of a one per cent, 

 aqueous solution of formalin. Wash in running water at least one hour and then 

 differentiate in 



Saturated alcoholic solution of picric acid - 1 part. 



Water -------- 1 part. 



Alcohol (94 per cent.) ----- 2 parts. 



The differentiation will generally require only a few seconds. Rinse in 75 

 per cent, alcohol and examine ; if still too deeply stained, transfer again to the 

 differentiating solution, and so continue until the stain is clear and sharp, then 

 wash in running water for an hour, transfer to 50, 75, 94 per cent, and absolute 

 alcohol, clear in toluol, and mount in dammar. 



From such preparations the following conclusions are drawn : The " Cen- 

 tralkorper," or central body of the Cyanophyceae is a nucleus. The most impor- 

 tant reason for this conclusion is the behavior of the central body during cell 

 division. In all cells of the Cyanophyceae, except the heterocysts, the nuclei of 

 which degenerate very early, a single nucleus is present, its form depending 

 largely upon the shape of the cell. The resting nucleus consists of a slightly 

 staining ground mass in which are embedded numerous deeply staining granules. 

 These granules from their behavior during division, their reaction to stains and 

 digestive fluids, are to be identified with the chromatin granules of higher plants. 

 They are not the " red granules" of Biitschli. The nucleus differs from that of 

 higher plants in not possessing a nucleolus or nuclear membrane. During 

 nuclear division the granules fuse into chromosomes which separate as division 

 proceeds. Strands which represent spindle fibers may be seen between the 

 separating groups. The wall first appears as a ring midway between the daugh- 

 ter nuclei and gradually grows toward the center until the partition is complete. 



The writer believes that he has shown positively that the " Centralkorper " 

 is to be identified with the nucleus of higher plants. 



It is interesting to note that Zacharias, in a lengthy and — in our opinion — 

 somewhat prejudiced review of Dr. Hegler's paper (Bot. Zeit. 59 : 322-327, 1901) 

 disputes the accuracy of these conclusions and insists that there is no nucleus in 

 the Cyanophyceae. c. j. c. 



