10 NEW ZEALAND NATURE-STUDY BOOK 
stem of a leafy branch in water coloured with eosin 
it will be seen that the colouring matter in a short time 
has found its way into the mid-ribs, and through the ribs 
and veins into the softer part of the leaves. From this we 
learn that, in addition to acting as supports to the leaves, 
the mid-rib and ribs form a complete system of channels by 
Fig. 7.—Lime leaf. 
means of which the food absorbed by the root is distributed 
through the softer parts of the leaf. The starch and other 
food-materials formed in the leaf are moreover drained off 
by other passages which are bound. up with these channels. 
Colour of Leaves. In general the colour of the leaf 
is green, though the shade may vary considerably, and the 
under surface is much lighter in colour than the upper. 
