14 THE VEGETABLE KINGDOM. 



single cells of varied form, examine for yourself thus : 

 Take a flower, a few bits of stalk, a lily leaf, or small piece 

 of rhubarb stalk, another of cucumber, a thin slice of raw 

 potato, a wallflower, or a primrose any flower: macerate 

 it in water for a day or two, until it begins to decompose, 

 and the smallest portion placed under the microscope with 

 a drop of water will show you the now separating cells of 

 various shape : those in stalks oblong or cylindrical ; those 

 in the surface of petals and leaves square, or round, or 

 hexagonal, or irregular, with zigzag boundaries, or papilli- 

 form, as in the Geranium, Sweetwilliam, &c. ; those of the 

 parenchyma or pulp of the leaf generally oval. In looking 

 at these, you will certainly find a variety of contents which 

 are seldom preserved for any length of time, and which you 

 must, therefore, observe in the fresh and living plant. 



CELL-CONTENTS. 



In the slice of potato you will find every cell crowded 

 with starch- granules, that is, if it is a good potato; for starch 

 is to the potato what fat is to an animal, and if it is in 

 " good condition" the cells should be full of it. The test 

 of this is a drop of tincture of iodine, which turns the starch 

 granules to a beautiful blue or violet colour ; and a diseased 

 potato with empty cells will therefore be detected by a drop 

 of that same iodine. 



In the stem of a lily you will find starch-grains, mixed 

 with green granules of chlorophylle, a kind of vegetable wax, 

 which gives the green colour to leaves. 



All our farinaceous plants contain abundance of starch, 

 especially wheat, barley, oats, maize, rice, arrow-root ; and 

 the granules differ from each other in size and form so 

 decidedly, that they cannot well be mistaken by a careful 

 observer. They are prepared for the microscope, and sold 

 as polariscope objects, because the examination of a starch 

 granule with polarized light shows it with a beautiful black 

 cross, revolving with the polarizer; or, if over a selenite 

 stage, a brilliant play of colours is obtained. 



Besides starch-grains and chlorophylle, you will find 



