8 



YORKSHIRE NATURALISTS* UNIuN. 



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or expanded into a circle. They are arranged spirally on ihe 

 stem, and their density depends on the number in each spiral ; 

 when most distant they form two opposite rows, or are distichous, 

 represented by the symbol h, or two leaves in one circuit ; if 

 tristichous, -J- ; or the phyllotaxis may be -| or §, etc. 



If we remove a leaf or two, and place in water on a slide, 

 we find most frequently there is a central mid-rib or nerve, 

 variable in length, and often extending beyond the point as a 

 hair, or there may be two short ones; the margin maybe entire 

 or serrated, or with a thickened border. 



We also see that in most species the cells composing the 

 lamina of the leaf are in a single stratum, and that they vary in 

 size and form in different species, but are remarkably constant 

 in the same species ; they are of two principal forms, parcncJiy- 

 matous when square, rectangular, or hexagonal, so that the ends 

 are truncate, 7mA prosciichyinalous when elongated with the ends 

 triangular. The walls of cells often become thickened by 

 internal deposit, so that they appear like round dots, and are 

 termed incrassate, and pores in the walls also enable adjacent 

 cells to communicate. The external face of the leaf-cells may 

 also be the seat of local deposit and we get papilla:^ or warts 

 formed, and occasionally the nerve presents out-growths in form 

 of laminae or filaments. 



The reproductive organs are arranged in what are usually 

 called flowers, a term scarcely applicable, and for which I use 

 that of inflorescence ; this varies in position and constitution, 

 and is often so small as to be found with difflculty; it is terminal 

 when it ends in the main axis, and the small leaves enclosing 



f'/ 



i. 



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V 



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V>oU Truns. Y.N.U., 1891 (pub. 1806). 



