58 
Rev. T. A. Jefferies. 
the tussock whose roots were found to contain chlorophyll (see above, 
p. 56). The disappearance of the soil from the exposed side left the 
plant with more moisture in the humus collected in the body of the 
tussock itself than in the root region below, with the result that the 
new outer roots were found to be growing horizontally towards the 
centre of the plant and away from light and air (see Fig. 4). 
Several of the rhizomes had elongated an internode and grown 
upwards past the thickest part of the swellings on the shoots, so 
that the roots came off more than a cm., in one case over 2 cm. 
higher than the preceding ones and at a level where the shoots 
were sufficiently loosened to make way for the roots. In order to 
achieve this upward movement of the rhizomes, internodes were 
extended ten to twenty times their usual length, and the level at 
which the roots started was thereby permanently altered. Other 
cases recently investigated show that such elongation is by no 
means rare, but is to be regarded as the normal method of 
upbuilding when it is necessary for the tussock to ascend. It occurs 
where plants have been partly buried with ash after burning of the 
moors, and tussocks developing in a flush show the elongation 
repeated year after year, the roots coming off at successively higher 
levels, till the plant is lifted ‘well out of the water (see Fig 1 r, b.o., 
and b.d.) 
Sections of the rhizome, as might be expected from what has 
been said of their macroscopic form, generally show a confused 
tangle of vascular bundles crossing the section in all directions. 
The structure is simplified, however, where elongation has taken 
place, and is found to consist of the following: the surface is 
protected by a small celled cutinised epidermis, stiffened by a band 
of sclerenchyma two or three cells deep ; parenchyma follows 
varying in depth from five to ten medium sized, irregularly arranged 
cells, not rows of cells as in the cortex of the cord roots ; the 
endodermis and pericycle are of small cells, within which lies a 
ring of vascular bundles whose xylem elements are abundant and 
thick walled; the middle is occupied by a pith similar in appearance 
to the cortex. Usually the cells of the cortex and the pith are 
crowded with small starch grains, and this supply of reserve food is 
occasionally increased, as in the cord roots, by thickening of the 
cellulose walls of the starch containing cells. 
III. Erect Aerial Stem. 
The leafy stem of Molinia (see Fig. 1) is normally straight, 
thin except at the base, erect, glabrous and long, rising as already 
