CHAPTER V 



TEMPORARY MOUNTS AND MICROCHEMICAL TESTS 



Skill in making freehand sections, without any microtome, and in 

 teasing with needles, and in making dehcate dissections under the 

 simple microscope are absolutely necessary in any investigation deal- 

 ing with the structure and development of plants. Preliminary study 

 with the aid of such methods not only gives a broader view of struc- 

 tures in all dimensions and helps the interpretation of stained micro- 

 tome preparations but is necessary in determining whether material 

 is worth all the labor of making permanent mounts. That particular 

 class of temporary mounts intended only for chemical tests is con- 

 sidered separately in the second part of this chapter. 



TEMPORARY MOUNTS 



A preliminary examination of almost any botanical material may be 

 made without any fixing, imbedding, or staining. If a little starch be 

 scraped from a potato, and a small drop of water and a cover-glass be 

 added, a very good view will be obtained, and if a small drop of iodine 

 solution be allowed to run under the cover, the preparation, while it 

 lasts, is better than some permanent mounts. The unicellular and fila- 

 mentous algae can be studied quite satisfactorily from such mounts. 

 The protonema of mosses and the prothallia of ferns should be studied 

 in this way, even if a later study from sections is intended. The addi- 

 tion of a little iodine identifies the starch and makes the nucleus more 

 plainly visible. If the top of a moss capsule be cut off at the level of 

 the annulus, a beautiful view of the peristome may be obtained by 

 simply mounting in a drop of water, or, in a case like this where no 

 collapse is to be anticipated, the object may be mounted in a small 

 drop of glycerin — just enough to come to the edge of the cover without 

 oozing out beyond — and the preparation may be made permanent by 

 sealing with balsam, gold size, or any good cement. The antheridia 

 and archegonia 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 



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