9 2 



GROWTH AND WORK OF PLANTS 



of a soft and plasmic nature, in the protoplasm.* The chloro- 

 phyll is a green pigment in these bodies where it exists in numer- 

 ous very fine grains. The chloro- 

 phyll bodies lie in the outer layer 

 of protoplasm, next the cell wall. 

 They are distributed throughout 

 tne cells of the loose parenchyma, 

 the palisade cells, and the guard 

 cells, rarely in the epidermal cells, 

 and are absent from the vascular 

 bundles. 



2. MODIFICATIONS OF LEAVES. 



148. The normal form of the 

 leaf, as stated in the previous 

 chapter, is a broad, thin organ 

 which thus exposes to the air and 

 light a great surface in comparison 

 with its bulk. This is because the 

 normal work of the leaf is most 

 advantageously and economically 

 carried out with this form. There 

 are, however, numerous exceptions 

 to this form presenting what are 

 termed modifications of leaves in 

 different plants. These modifica- 

 tions are shown under a variety of 

 conditions: first, when the leaf has 

 entirely lost its normal function; 

 second, where a modification is 

 demanded to enable the leaf to resist the trying arid climate of 



* Chromatophore is a general name for these bodies. They are capable of 

 division, and thus grow and multiply in the plant as the cells increase. 

 When devoid of color they are leucoplasts, when they have the chlorophyll 

 green they are chloroplasts, when they have red or yellow pigments they are 

 chromoplasts, as in the red and yellow petals of flowers, in the carrot, etc. 



Fig. 77. 



Indian pipe plant (Monotropa uniflora) 

 with white stems and white scale leaves. 



