52 ELEMENTARY BIOLOGY. [VI. 



by the colourless band, in which no movements 

 occur. Try to find the nucleus; it has usually 

 disappeared in cells in which currents have com- 

 menced, but when present is passive and carried 

 along by them. Sometimes it is very difficult, 

 on account of the incrustation of the leaf-cells of 

 Chara, to make out the protoplasmic movements 

 in them ; if this is found to be the case, the 

 manubrial cells from an antheridium should be 

 used instead. 



1. Tradescantia. Examine in water, with a high 

 power, the hairs which grow upon the stamens : 

 they consist of a row of large roundish cells, each 

 with sac, protoplasm, nucleus, and vacuolar 

 spaces. Note the protoplasm ; partly forming a 

 layer (primordial utricle) lining the sac, and 

 heaped up round the nucleus, and partly forming 

 bridles running across the cell in various di- 

 rections from the neighbourhood of the nucleus 

 and from one part of the protoplasm to another ; 

 observe the currents in these bridles; from the 

 nucleus in some, towards it in others. 



c. Vallisneria. Take a leaf beginning to look old ; 

 split it into two layers with a sharp knife and 

 mount a bit in water; examine with a high 

 power. Note the larger rectangular cells, be- 

 longing to the deeper layers, with well-marked 

 currents in them, which carry the chlorophyll 

 granules round and round inside the cell-wall. 



If no currents are seen at first, gently warm 

 the leaf by immersing it for a short time in water 

 heated to a temperature between 30 and 35 C. 



