Temporary Mounts and Microchemical Tests 73 



of mosses may be examined if the surrounding leaves are carefully 

 teased away with needles. Freehand sectioning with a sharp razor 

 and judicious teasing with a pair of needles will give a fair insight into 

 the anatomy of the higher plants without demanding any further 

 knowledge of technic. This rough work is a very desirable ante- 

 cedent to the study of microtome sections, because most students see 

 in a series of microtome 



sections only a series of | 



sections when, in the 



FIG. 15. The hanging-drop culture. 



mind s eye, the}- ought 



to see the object building itself up in length, breadth, and thickness 



as they pass from one section to another. 



The movements of protoplasm can, of course, be studied only in 

 the living material. Every laboratory should keep Chara growing 

 at every season of the year. Mount a small portion and note the 

 movements in the internodal cells. Avoid any pressure and any 

 lowering of the temperature. A gentle raising of the temperature 

 will accelerate the movements. Elodea shows the movements very 

 clearly, especially in the midrib region. The stamen hairs of Trades- 

 cantia have long been used, their color, resembling a faint haema- 

 toxylin stain, making them particularly favorable. Stinging hairs 

 show a brisk movement if they are mounted quickly and without 

 injury. Fortunately, the common onion always furnishes favorable 

 material for demonstrating the movements of protoplasm. Strip 

 the epidermis from one of the inner scales of the bulb and mount 



in water. The 



i VMwmmw .j granules may 



appear to better 



FTG. 16. Another hanging-drop culture. 



advantage in 

 yellow light, like that of an ordinary kerosene lamp. 



The germination of spores and the growth of pollen tubes can 

 be studied in the hanging drop. For facilitating such cultures 

 there are many devices, such as hollow-ground slides, glass rings, 

 rubber rings, etc. (Fig. 15). A device which is better for most 

 purposes, and which is easily made by any student, is shown in 

 Fig. 16. 



