ORGANS OF FLOWERING PLANTS 15 
it forces its way through the soil. The root tip must. 
at times exert enormous force, for it penetrates the 
hardest soils, even the cement-like clays so common 
in some parts of New Zealand forming no bar to its. 
progress. For fear that the root hairs and root caps 
may have been broken off or injured in removing the 
bean plant from the soil, place a number of barley 
grains and mustard seeds to germinate between layers 
of moist flannel. These will show abundance of root 
hairs (Fig. 4) and will exhibit the root-cap distinctly 
outlined as a conical transparent mass at the extreme 
tip, behind which may be seen the denser tissue of the 
erowing point, 
Nodules. On the roots of the bean will be noted 
little fleshy swellings forming the well known nodules 
or tubereles. These are peculiar to plants belonging 
to the bean family, and their significanee will appear 
later on. 
2. The Stem. (Fig. 1). The objects of the stem are: 
(a) To place the leaves in positions in which 
they can get most air and sunlight. 
(b) To display the flowers so that insects may 
readily see them. 
(c) To place the fruit in the positions most 
suitable for distribution, whether by wind, 
water, birds or other animals. 
(d) To afford a passage from root to leaf and 
thus connect the latter with the soil. 
The stem, then, is the great helping organ of the 
plant. The root, to fulfil its functions, must make its 
way downwards and explore the soil: the stem, to give 
the help demanded, must make its way upwards to the 
air and sunlight. 
Observe that, unlike the root, the stem is jointed. 
Each joint is called a node (Fig. 1) and the space 
between, an internode (Fig. 1). Here again we may 
