356 HOFMEISTER, ON 



is reckoned not with reference to the longitudinal axis of the 

 stein, but to a plane passing through this axis and the in- 

 dentation of the stem, in which plane the points of origin of 

 the roots are situated. 



The tissue of the region of the stem in which the 

 closely crowded horizontal places of origin of the vascular 

 bundles of the leaves meet together, goes to form the 

 upward-growing portion of the proportionably slight woody 

 mass which occupies the longitudinal axis of the stem, but 

 encloses no pith. 



In the germ-plant, as long as the h arrangement of 

 the leaves lasts, this upper half of the woody mass has a 

 two edged form. Its usually spindle-shaped cells — reti- 

 culated and spiral cells mixed with a few delicate walled 

 cells — have almost all the same direction ; they are parallel 

 to the larger transverse diameter of the woody mass (PI. 

 XLVIII, figs. 2, 3 ; PL XLIX, fig. V). A longitudinal sec- 

 tion through the furrow of the stem cuts all the wood-cells 

 transversely. As the arrangement of the leaves passes 

 through the | into the §, §, T 5 3 , and £ arrangements, the 

 upper part of the woody mass becomes round, and the di- 

 rection and form of its cells very various, appearing at first 

 sight to have no regularity, owing more particularly to the 

 fact that now many other cells besides the primary cells of 

 the vascular bundles take part in the wood-formation. 

 Spiral cells are also formed which are situated between the 

 converging rudimentary portions of the vascular bundles ; 

 by this means the woody mass is closed up to the form of 

 a cylinder. 



The closely crowded points of origin of the roots repre- 

 sent the under half of the woody mass : a row of spiral 

 cells concave above, at right angles to the larger horizontal 

 axis of the upper mass of wood, which latter in the first 

 year is two-edged. 



At the close of the first vegetative period of the germ- 

 plant the cells of the bark are filled with amyloid granules, 

 mixed with a few oil-drops. The cells, however, which 

 immediately surround the mass of wood retain their capa- 

 city for multiplication. Some time before the commence- 

 ment of the first period of winter-rest they have divided 



