MICROSCOPE IN THE GARDEN. 23 



under the Microscope. The starch granules are 

 insoluble in water, but they are easily diffused 

 through it ; so that by washing any vegetable tissue 

 containing starch, with water, and pouring it off 

 and allowing it to stand, the starch falls to the 

 bottom. In this way the various kinds of starches 

 may be procured for microscopical examination. 

 The granules of starch have frequently a little 

 black irregular spot in their centre. In the starch 

 of Indian corn it assumes the form of a cross 

 (Fig. 61, PL 3). Starch is a good object for the 

 use of the polarizing apparatus, which can be 

 applied to most compound Microscopes. The 

 grains of starch, under the influence of polarized 

 light, become coloured in a beautiful and peculiar 

 manner, permitting of great variation, as in the 

 case of all polarized objects. 



If we take a little of the white juice from the 

 common dandelion, and put it under the Micro- 

 scope, we shall often see, besides the globules of 

 caoutchouc which makes the juice milky, crystals 

 of various forms. Such crystals are called by the 

 botanist "raphides," signifying their needle-like 

 form. They arise from the formation and accu- 

 mulation of insoluble salts in the fluids of the plant. 

 They are seen in various plants, and under very 

 different circumstances. Beautiful needle-like crys- 

 tals can be seen in the juice of the common hyacinth 

 (Fig. 64, PL 3), which may be obtained by pressing. 

 A question has been raised as to whether they are 

 always formed in the cell. They are mostly found 

 lying in the cell, as in the leaves of the common 

 aloe (Fig. 65, PL 3) : they may also be seen in 

 the tissues of the common squill, and in the root 

 of the iris. If a thin section of the brown outer 

 coat of the common onion is made, small prismatic 

 crystals are observed (Fig. 67, PL 3). Sometimes 



