38 A HALF-HOUR WITH THE 



action of a little solution of caustic potash, they 

 may frequently be seen to be slightly pitted. This 

 is represented from cork in figure 59, plate 3. 



Many of the structures which are described above 

 may be seen in common coal ; thus proving most 

 satisfactorily that this substance has been formed 

 from a decayed vegetation. A transverse and a 

 longitudinal section of coal is shown at figures 60 

 and 61, plate 3. The examination of coal, how- 

 ever, is by no means an easy task, and the hands 

 and fingers may be made very black, and the 

 Microscope very dirty, without any evident struc- 

 ture being made out. Some kinds of coal are 

 much better adapted for this purpose than others. 

 Sections may be made by grinding, or coal may be 

 submitted to the action of nitric acid till it is 

 sufficiently soft to be cut. The amateur will not 

 find it easy work to make sections of coal ; but 

 should he wish to try, he may fasten a piece on to 

 a slip of glass with Canada balsam, and when it 

 has become firmly fixed, he may rub it down on a 

 fine stone till it is sufficiently thin to allow its 

 structure to be seen under the Microscope. Coal 

 presents both vascular and cellular tissue. The 

 vascular tissue is, for the most part, of the glandular 

 woody kind; thus leading to the inference that 

 the greater portion of the vegetation that supplied 

 the coal-beds belonged to the family of the firs. 



The external forms of the tissues of plants 

 having been examined, we are now prepared to 

 regard their contents. In the interior of the cells 

 forming the roots and the growing parts of plants 

 will be observed a number of minute grains, 

 generally of a roundish form. If we make a thin 

 slice of a potato, these granules may be very ob- 

 viously seen, lying in the interior of the cells of 

 which the potato is composed, as seen at figure 64, 



