2028 Journal of Applied Microscopy 



r NEWS AND NOTES. J 



Mounting Objects for Temporary Study. — Objects which are to be ex- 

 amined only temporarily may be mounted in water or, if it is preserved material, 

 in a drop of the preservative. Alcohol and formalin, however, evaporate too 

 rapidly to serve for more than very short observation. Normal salt solution 

 (.6 gram common salt in 100 c. c. water) serves well for a great many objects. 

 Whenever living objects, such as micro-organisms, are to be examined, they 

 should be mounted in the natural medium, as a change of medium may retard 

 the activities of the organism. If too much liquid is placed on the slide, the 

 cover, when dropped into place, will float about, or the specimen may tioat out 

 from under the cover. Surplus liquid should be removed with a cloth or blotting 

 paper until the cover remains in position, even when the slide is inclined. On 

 the other hand, if too small an amount of liquid is placed on the slide or too 

 much withdrawn, the specimen, if it be a soft object, may be crushed. The cover 

 should not be allowed to fall upon the drop of medium, for one is then unable to 

 control the position of the specimen and air bubbles are apt to be formed. The 

 cover should be held with fine forceps and one edge brought in contact with the 

 liquid, then gradually lowered into position, with the object as near the center 

 of the field as possible. To prevent evaporation of the medium, if one wishes to 

 keep the specimen for some time, the cover may be sealed to the slide with a 

 ring of vaseline or castor oil. 



On the Teaching of Plant Physiology to Large Elementary Clas- 

 ses.* — Until each student can be supplied with apparatus for the various 

 experiments in plant physiology, the presentation of the subject to large 

 classes will be more or less difficult and unsatisfactory. It is generally 

 agreed that, in elementary work, eight to twelve conclusive and practicable 

 experiments upon the most fundamental subjects, as photosynthesis, respi- 

 ration, osmotic absorption, etc., are sufficient. Professor Ganong's plan for 

 meeting the difficulties involved and attaining the end desired, is as follows : 

 " I try first to make sure that the importance and general bearing of the problem 

 to be studied is clearly before them ; in fact, I try to make the experiment seem, 

 as it really is, not only a logical but a necessary step in their progress. Then I 

 set up the experiment from the very beginning, explaining the reason for each 

 step and for the use of each piece of apparatus, the action of each chemical, and 

 the physical principles involved. The students follow, asking what questions 

 they wish, making full notes and sketches, etc. The completed arrangement is 

 then placed in the laboratory, and each student makes individual records of the 

 observable results. When the results are complete, or when the result depends 

 upon some special test to be applied, the experiment is again brought before the 

 class ; the tests are applied and results discussed. A mimeographed synopsis of 

 the experiment, including the theory of the method, and giving such statements 

 of fact as are essential to the full grasp of the subject, is then supplied to them, 

 and from these various sources they are expected to prepare a synoptical, illus- 

 trated exposition of the object, method, results and bearings of the experiment. 



c. w. J. 



* Gaaong, W. F., Smith's College. School Science, 1 : 9. 



