MICROSCOPE IN THE GAPXEN. 45 



at figure 126. In the passion-flower, three rings 

 are observed upon them, as though they had been 

 formed with a turner's lathe — figured at 127. In 

 the common mallow, they are covered all over with 

 little sharp-pointed projections, like a hand-grenade. 

 These are represented at figure 128. The micro- 

 scopic observer should make himself acquainted 

 with the forms of pollen grains, as, on account of 

 their small size and lightness, they are blown about 

 in all directions, and may be found on very dif- 

 ferent objects from those in which they have been 

 produced. Some absurd mistakes have been com- 

 mitted by confounding pollen grains with other 

 forms of organic matter. Thus, pollen grains in 

 bread were regarded as bodies connected with the 

 production of cholera. 



The pistil, which is the central organ seated in 

 the midst of the stamens in the flower of plants, 

 will afford a great variety of interesting points for 

 examination with the Microscope. In the earliest 

 stages of the growth of the pistil, thin sections of 

 it may be made, and the position of the ovules 

 observed. In the ovule will be found the embryo 

 sac, a central cell, which, on being brought in 

 contact with the pollen grain, grows into the seed. 

 The seed contains the embryo, or young plant. In 

 most plants this is sufi^ciently large to be seen 

 by the naked eye ; but it may, nevertheless, be 

 examined with advantage by a low microscopic 

 power The seed is covered on the outside with 

 a membrane, which is called the " testa." This 

 membrane is often curiously marked, and the whole 

 seed may be examined as an opaque object with 

 the low powers of the Microscope. In order to do 

 th>s, the light must be shut off from the mirror, 

 and, the object being placed on the stage, a pencil 

 of light should be thrown upon it by the aid of the 



