LECTURE I. 



IT is convenient to begin the study of plants with the simplest. 

 The most simple are as a rule the smallest. 



To make out the structure of these very small plants the use of 

 a microscope is essential. Hence we commence our course by 

 learning how to use a microscope. Here on the screen is a figure 

 which will give you the names of the different parts of a micro- 

 scope. 



Set the instrument on a table opposite a window, preferably one 

 facing the north. The pillar of the microscope should be placed 

 next the observer. Turn the mirror so that the light from the sky 

 is reflected upwards from the plane surface of the mirror through 

 the aperture in the stage up the body of the microscope. See 

 that the iris-diaphragm below the condenser is open and that the 

 low objective (or power) is in position at the lower end of the tube 

 (or body). With these preliminary arrangements made, it will be 

 well to apply the microscope to some suitable object and learn 

 something of how it may be used to show minute structure. It 

 must be understood that, as the microscope extends our powers of 

 vision, so as practically to endow us with a new sense, this new 

 sense, like our other senses, requires training and cultivation, and 

 it is only after considerable practice that we can interpret truly 

 the sensations conveyed to us by this instrument. 



A very suitable object for the beginning of this training is 

 furnished by the skin of a leaf. We will select the leaf of Tra- 

 descantia virginiana (Spiderwort). To obtain a preparation of 

 this skin, proceed as follows : take the leaf, which is long and 

 narrow, and bend it across the fore finger of the left hand with 

 the upper, or grooved, side outwards. With a sharp knife, or razor, 

 nick the surface of the leaf without cutting deeply into it. Raise 

 a little flap of skin, the leaf-skin, and catch it with a forceps. 

 You will in this way easily peel off a portion of the membranous 

 skin. Lay the piece of skin so obtained in a drop of water on a 

 glass slide. The smooth upper side of the skin should be laid 

 uppermost in the drop. Clean a cover-glass like this one I hold 



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