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PRACTICAL BOTANY 



divisions in the dermatogen are all anticlinal, those in the 

 lower layer are both periclinal and anticlinal. (Compare 

 Fig. 6.) As they increase in size their internal tissues 

 become differentiated into (1) procambium, which is 

 subsequently connected with 'that of the stem, and (2) 

 tissue with intercellular spaces, which is continuous 



FIG. 6. Diagram illustrating the mode of origin of leaves (with alternate arrange- 

 ment) from the growing point of a Phanerogam. A, apex of the growing point. 

 B, c, D, various stages in the origin of a new leaf: the arahic numbers, and 

 shading, indicate how the individual layers of cells take part in the origin of the 

 new leaf. It is clearly indicated in ttds diagram that no periclinal divisions 

 appear in the cells of the dermatogen. (After Sachs.) 



with the cortex. At the same time single cells ot 

 the dermatogen grow out, and divide, so as to form 

 the conical multicellular hairs, which cover the sur- 

 faces of the leaves. In the older leaves of the bud the 

 development of the emergences around and below the 

 bases of these hairs may be traced : these are not 

 represented in the diagram (Fig. 6). 



