TEMPORARY MOUNTS AND MICROCHEMICAL TESTS 81 



insight into the anatomy of the higher plants without demanding any 

 further knowledge of technique. This rough work is a very desirable 

 antecedent to the study of microtome sections, because most students 

 see in a series of microtome sections only a series of sections when, in 

 the mind's eye, they 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. A leaf of Elodea shows the movements very clearly, 

 especially in the midrib region. The stamen hairs of Tradescantia have 

 long been used, their color, resembling a faint haematoxylin stain, 

 making them particularly favorable. Stinging hairs show a brisk move- 

 ment if they are mounted quickly and without injury. Fortunately, 

 the common onion always furnishes favorable material for demon- 

 strating the movements of protoplasm. Strip the epidermis from one 

 of the inner scales of the bulb and mount in water. The granules may 

 appear to better advantage in yellow light, like that of an ordinary 

 kerosene lamp. 



In studying the movements of protoplasm, a drop of aqueous car- 

 mine, allowed to run under the cover, will bring the protoplasm more 

 clearly into view. The protoplasm is often so nearly colorless that one 

 recognizes it only by the movement of plastids and various granules 

 which are carried along in the current. 



The discharge of spores and gametes should be observed in the liv- 

 ing material : the difference in the behavior of spores and gametes is 

 very striking and can be appreciated only while they are alive. Most 

 aspects of growth and movement can be studied best in the living con- 

 dition. In short, it is well to make a preliminary study of everything. 



The development of the micromanipulator has brought such an 

 immense improvement in the technique of studying living material 

 that some investigators can make tiny glass needles which they can 

 insert into a cell, hook a needle into each end of a chromosome, stretch 

 it, and allow it to contract. This remarkable instrument, which can be 

 used with any high-grade microscope, opens an attractive field for 

 work in cytology and microchemistry. 



The germination of spores and the growth of pollen tubes can be 



