156 ACTION OF AMMONIUM MOLYBDATE, ETC., 



several agents with a view to exhibit the contracted condition of 

 the protoplasm in vegetal cells. 



The best plant I have met with, and one well suited for class 

 demonstration, is the Tradescantia virgitiica, or American Spider- 

 wort. The cuticle of the inferior surface of the leaf, carefully 

 peeled off and treated with various reagents, readily exhibits the 

 protoplasm contracted in the cells, with fine fibrils reaching out to 

 the cell-walls. The sepals, also, prepared in the same way, exhi- 

 bit this condition very beautifully. Arum also exhibits these 

 changes very well. At first, I used the Sulpho-Cyanide of Potas- 

 sium, but this agent acts too rapidly in most cases, unless much 

 diluted, as the protoplasmic mass completely detaches itself from 

 the cell-walls and assumes a globular form, without presenting any 

 fibrils connecting it to the cell-wall. Another plan is to employ 

 salt, as mentioned by Mr. Gardner, and having obtained the 

 change in the protoplasm, wash out the salt by the addition of 

 water to the specimen, and then add a solution of Ammonium 

 Molybdate, and watch the effect. 



In Tradescantia^ this chemical agent usually leads to a feeble 

 yellow tinting of the protoplasm ; so rendering it more visible in 

 its divided form. 



Ammonium Phosphate also exhibits the protoplasm in a con- 

 tracted state ; so also the Liquor Sodae Chlorinate of the Brit. 

 Pharmacopoeia, when diluted to one-tenth with water. Sulpho- 

 carbolate of Soda, followed by the Molybdate, gives a tint to the 

 protoplasm. The employment of the Sulpho-Cyanide is well 

 worth trial, as when this substance is applied to the epiderm cells, 

 apparently possessing no contents, a large globe of protoplasm is 

 seen to separate itself into the centre of the cell. 



The above-mentioned use of Ammonium Molybdate led me to 

 make further trial of its chemical action on the cells of leaves ; 

 and in consequence I have obtained some curious results in con- 

 nection with its employment. The Molybdic salt, by itself, will 

 generally attack the hypoderm (cells beneath the epiderm), and 

 tinge them of all shades of orange, from the palest yellow to a 

 deep-red orange. In some cases, this change is not brought out. 

 In others, where the reaction is weak, the colouration is vividly 

 brought out by the further addition of Sulpho-Cyanide of Potas- 



