228 Puget Sound Marine Sta. Pub. Vol. 1, No. 21 



or tissue, but unless the colors depend upon the formation of definitely 

 known compounds, they cannot add much to our knowledge of the mi- 

 crometabolism of the cell. However, if the reaction is dependent upon 

 the formation of characteristic crystals or precipitates with a definite sol- 

 ubilit}^, the results will be as conclusive as those obtained in gross qual- 

 itative analyses. 



Calcium. — The sections were placed in 3% sulphuric acid and al- 

 lowed to evaporate for several hours. Crystals of calcium sulphate were 

 formed (Figs. 8, 9, 10). Other methods tried were the precipitation of 

 calcium oxalate with ammonium oxalate, and of calcium carbonate with 

 ammonium carbonate. Neither of these methods produced distinctive crys- 

 tals ; only amorphous j^recipitates were formed. 



Magnesium. — The method given by Richter*' was found to be very 

 satisfactory. The sections were placed in a drop of .1% NaHNH^PO^-j- 

 I2H2O and placed in a damp ammonium atmosphere. After some time 

 small crystals of magnesium-ammonium phosphate were formed (Fig. 6). 



Sodium.- — The presence of sodium in the cell is demonstrated with 

 great difficulty. A good reaction, different from Molish" and Tunmann^, 

 was obtained when the sections were heated to about 60° C. for a half 

 hour in a 10% solution of uranium acetate, followed by an application of 

 ? drop or two of dilute acetic acid. Heating the sections probably caused 

 the solution to enter more rapidly. The sections were then allowed to 

 evaporate to almost complete dryness. Various sized crystals were 

 formed, the smaller ones were colorless and the larger ones light yellow. 

 In plant tissues, magnesium is the only metal that would cause an error 

 in the results. In this case sodium-magnesium-uranyl acetate would be 

 formed, which produces colorless rhomboidal crystals. A few such crys- 

 tals were formed. However, these also show the presence of sodium 

 (Figs. 1, 2). 



Potassium. — The most characteristic reaction of potassium is ob- 

 tained with platinum chloride, but as with sodium it is very difficult to 

 obtain crystals within the cell. The sections were placed in a 10% alco- 

 liolic solution of platinum chloride which was then allowed to evaporate, 

 ('rystals of potassium-chloroplatinate were formed; some inside the cell, 

 but a greater percentage outside (Figs. 4, 5). A quicker and easier method 

 was to use a solution of 30 gr. of cobalt nitrate and 25 gr. of sodium 

 nitrite in 75 cc. of dilute acetic acid. As soon as the reaction within the 

 solution ceased, 25 cc. of w^ater was added and the whole filtered. In the 

 presence of potassium a precipitate of potassium cobalt nitrite is formed 

 (Fig. 2). Ammonium compounds, however, react with this solution. 



6Richter, O. Sitzungsber. d. Kais. Akad. d. Wiss. i. Wien 3:171. 1902. 



