MICROSCOPE IN THE GARDEN. 37 



found in the garden rhubarb, at figure 47, plate 2. 

 Sometimes these vessels are found branched, as in 

 the common chickweed, which is seen at figure 50, 

 plate 2. This arises from two spires coming in 

 contact with each other, and adhering. Occasion- 

 ally the spiral fibre breaks, or is absorbed at certain 

 points, leaving only a circular portion in the form 

 of a ring, as seen in a vessel from the root of 

 wheat at figure 49, plate 2. Such vessels are 

 called "annular," and may be observed in other 

 roots besides those of growing wheat, as in the 

 leaves of the garden rhubarb. A modification of 

 this kind of tissue is seen in the stems and roots 

 of ferns, in which the vessel assumes a many-sided 

 form. This kind of tissue is called " scalariform," 

 or ladder-like, and is seen in figure 52, plate 2. 

 Sometimes the spiral fibre is free. This is repre- 

 sented at figure 250, plate 8, from the testa of the 

 seed of the wild sage. 



The bark as well as the wood of trees affords the 

 same appearance under the Microscope. If a piece 

 of the bark of any plant be examined by means of 

 a very thin transparent section, and placed upon a 

 slide, and put under an inch or a half-inch object- 

 glass, the structure of the bark may be easily seen. 

 On the outside of all is the cuticle, or epidermis, 

 and under this lie two layers, composed, like the 

 cuticle, of cellular tissue ; but the inner layer, 

 before we come to the wood of the stem, is com- 

 posed of woody tissue. The cellular layer, next the 

 woody one, is often developed to a very great extent, 

 and then constitutes what we know by the name of 

 cork. The bark from which corks are made is 

 obtained from an oak tree which grows in the 

 Levant. If we make a very thin section of a cork, 

 its cellular structure can be easily made out. The 

 cells are almost cubical, and when submitted to the 



