CHLOROPLASTS AND CHLOROPHYLL 



105 



FIG. llo. Upper epidermis and palisade cells of 

 a buttercup leaf 



A, section perpendicular to upper surface; B, exte- 

 rior view of upper surface with palisade cells seen 

 through epidermis : e , epidermis : p, palisade cells. 

 Much magnified. After Bonnier and Sablon 



walnut leaf about 

 300,000 per square 

 inch of the lower 

 epidermis. 



124. The meso- 

 phyll ; chloroplasts ; 

 chlorophyll. The 

 mesophyll appears to 

 the naked eye of a 



o 



uniform green, but 



under the microscope 



its cells are seen to 



contain many green 



structures called chlorophyll bodies or chloroplasts (" chlorophyll" 



meaning leaf green and " chloroplast ' meaning molded out of 



green material). The color of the leaf, as well as that of green 



stems and other parts of the plant body, is due to these. A 



chloroplast is usually, in seed plants and 



in the higher spore plants, of an ellipsoidal 



form or lens-shaped 



and somewhat 



translucent. Its 



color is due to a 



green substance, 



soluble in alcohol 



but not in water, 

 a buttercup (diagram- known as chloro- 



w- 



e- 



w-\\. 



FIG. 116. Passage of a 

 fibre-vascular bundle 

 from stem to leaf of 



matic) 



s, stem; w, woody part of 

 bundle : &, sieve cells of 

 bundle. After Bonnier 

 and Sablou 



phyll 



125. Woody tis- 

 sue in leaves. The 

 veins of leaves con- 

 sist of fibre-vascular bundles containing 

 wood fibers and vessels much like those 

 of the stem of the plant. Indeed, these 

 bundles in the leaf are continuous with 



FIG. 117. Diagram of 

 distribution of fibro- 

 vascular bundles in the 

 leafstalk of a buttercup 



e, epidermis; w, woody 

 part of bundle ; b, sieve 

 cells of bundle ; /, fibrous 

 layer on outer part of 

 bundle. Magnified. - 

 After Bonnier and Sa- 

 blon 



