34 
these veins are the passages through which the sap 
of the plant is conveyed into the leaf. There is a 
“ main ” (the mid-rib) 
along which sap passes, 
and thence it flows into 
veins and veinlets to be 
uniformly distributed. 
We can easily conceive, 
looking at the metho¬ 
dical manner in which 
every thing in nature 
is arranged, that such 
ramifications will be 
placed in the same man¬ 
ner on both sides ; the 
object they have to 
serve on either side being the same. 
75. Sometimes leaves do not stand precisely in the 
same position with regard to the stem as in common 
cases. If we examine a laurel, we find that the 
leaves are so placed that the planes formed by the 
upper and lower surfaces are presented, the one to 
the sky, the other to the ground; and so it generally 
is. But in some plants it is otherwise, and this differ¬ 
ence so affects the whole character of the plant that 
the distinction becomes of great importance. 
76. In certain instances, that of the Iris for ex¬ 
ample, the edges are turned upwards and downwards, 
so that the planes of the leaf are at right angles to 
the earth. This circumstance cannot escape notice in 
such a plant as an Iris, but it occurs not uncommonly 
also among trees, when it may be easily overlooked. 
77. There is a graceful race of plants inhabiting 
New Holland, in which every leaf is placed so that 
SYCAMORE LEAF. 
