17 



bee's-wax. The exhibition jar is filled with a mixture made up 

 of 50 cc. saturated solution of sodium carbonate, 25 cc. satu- 

 rated solution of dibasic sodium phosphate, and 50 grams of 

 calcium silicate. When the liquid is fairly clear small pieces of 

 calcium chloride are dropped to the bottom of the jar. In from 

 one to several hours the forms will arise from the chloride 

 particle (Figs. 1, 2, and 4). The structures may attain a height 

 of from a few to thirty or more centimeters. Their growth can 

 be checked and varied by carefully adding distilled water. By 

 very slowly moving the solution, branching and other variations 

 may be induced. When the desired structures are completed 

 the liquid may be slowly siphoned off, they are sufficiently hard 

 and rigid to stand by themselves in the air but are very brittle 

 and must be handled with care. Some of the aqueous cytologi- 

 cal stains if carefully poured over the bottom will add to the 

 attractiveness of the preparations. Carmine or light green will 

 diffuse to the tops of the structures without altering their form. 



If in the above preparations a very dilute solution of the 

 same mixture is added after the mimic organisms are formed 

 bladder-like enlargements will "grow" at the tips and increased 

 resemblance to plant forms may thus be obtained (Figs. 

 1 and 4). 



Other three dimensional imitations can be made by drop- 

 ping a mixture of equal parts of sugar and copper sulphate crys- 

 tals into a warm solution made up of 100 cc. distilled water, 10 

 grams gelatine, 10 cc. saturated solution potassium ferrocyanide 

 (yellow) and 10 cc. saturated solution of sodium chloride. Tree- 

 like trunks and branches, roots, leaves, and bud imitations are 

 formed. When the gelatine solidifies the preparation is perman- 

 ent and may be preserved and transported without injury. 



Attention should be drawn to the possibilities in soap bub- 

 bles for a study of contact and pressure relations in cell form. 

 Soap bubbles as is well known exhibit identical forms to those 

 of massed cells in a parenchyma. A square glass jar, about 

 quart size or larger, can be filled with soap bubbles by pouring 

 into it a little soapy water and then blowing into this with a 

 glass tube. The importance of surface tension and the principle 

 of minimal areas, mutual contact and pressure in the control 

 of cell form can here be pointed out. It can be shown to the 

 student that in a froth as well as in massed cells the walls meet 



