14 BOTANY. 



glass, noting the wateriness. Lay the specimen aside for half an 

 hour or so, and tlien note its shriuliage hy loss of water. 



(6) Mount a few plants of Pond Scum (Spirogyra) in a very little 

 water. Examine under the high power of ihe microscope, and while 

 doing this flow glycerine under the cover-glass. The glycerine im- 

 bibing water with great avidity withdraws the water of the cell-sap 

 from the cells, causing them to collapse. 



(c) The presence of sugar may be demonstrated in many cases by 

 taste alone, as in the stems of cane and Indian corn. 



((?) Cane-sugar when abundant may be crystallized out (in small 

 stellate crystals) from cell-sap by the use of strong alcohol or glyce- 

 rine. 



(e) Make thin slices of the root of the sunflower or dahlia, and soak 

 for some days in alcohol: the inulin will appear in the shape of 

 sphere-crystals of greater or less size, according as the crystallization 

 has been slower or more rapid. 



(/) The presence of acids in the cell-sap of many plants may be 

 shown by placing a moist cut surface in contact with blue litmus- 

 paper. The latter will be distinctly reddened. 



Note. — In the study of minute objects it is now the general cus- 

 tom to use metric measurements. The units used are the millimetre 

 and the micronlillimetre, the former for the larger measurements, the 

 latter for the smaller. A millimetre equals .0394 of an inch, or 

 nearly one twenty-fifth of an inch. 



For the measurement of objects requiring high powers of the 

 microscope the micromillimetre is used. It is represented by the 

 Greek letter /x, or by mmm. It is one thousandth of a millimetre, 

 and equals .0000394 of an inch, or nearly one twenty- five-thousandth 

 of an inch. A spore is thus said to measure 15 ix in diameter, 35 )i 

 in length, etc., or in the absence of the Greek letters we may record 

 these measurements as 15 mmm. and 35 mmm. In reading the fore- 

 going we may of course say 15 micromillinietres and 35 micromilli- 

 metres, but more commonly the contraction micro is used, or even 

 the name of the Greek letter: thus we may say 15 micros, or 15 mu. 



