10 
and immediately within it a harder and darker 
matter, which is tessellated, as if made up of minute 
fragments like mosaic. The little tessellations or 
black marks which constitute the dark stain that 
distinguishes this wood, are all curves, — dark curves, 
with certain holes or passages in their hollow. But 
the curious fact is this: the whole of the curves 
are placed in the same relation to the central part 
of the stem, their convexity being invariably directed 
to the circumference; and among the millions of 
little marks which form the natural structure of 
this plant, and represent its (internal) symmetry, 
every one is in the same relative position with 
respect to the centre. Beautiful patterns might 
indeed be made out of such bodies. The same thing 
occurs in the larger part of the order of Palm trees. 
I do not mean to say that there are no examples 
to the contrary; many disturbing causes indeed in¬ 
terfere with this arrangement; but if we can observe 
the curves in the position in which they were ori¬ 
ginally formed, the relation which they bear to each 
other is constant. Distortions and disturbances arise 
from peculiar growth or from accidental causes, 
which are without the pale of systematic inquiry, and 
not susceptible of being reduced to any fixed rule. 
17. And so with regard to the veins of plants; 
they too are always distributed in an exactly sym¬ 
metrical manner. Take any leaf. If we separate it 
from end to end (along the mid-rib), the one half 
bears a most striking resemblance to the other. On 
the one side the veins run to the right, on the other 
to the left: perhaps those to the right are a little 
above those to the left, in that case the difference is 
maintained throughout. If there are four ribs on the 
