LEAVES 119 
Sometimes stem-structures assume a very leaf-like 
form, as in the Butcher’s Broom (Ruscus aculeatus), 
where the ultimate branches are ovate and quite flat, 
and might be taken for true leaves but for the fact 
that they bear on their surface flowers, and subse- 
quently berries. The leaves themselves are in this 
plant reduced to minute scales, and from their axils 
these flattened branches spring. In fact, where leaf 
reduction takes place, the process of assimilation is 
often shared in varying degree by the leaves, the 
stipules, and the stems. Among our native plants, as, 
for instance, in the Leguminosze and Rosaceze, the 
reader may find for himself many interesting examples 
for examination. 
But the large majority of the Seed Plants bear well- 
developed leaves, to which the process of assimilation 
is practically confined. 
LEAVES vary surprisingly in size, shape, and arrange- 
ment, features which are closely related to the char- 
acters of the stems which bear them, the object being 
the most advantageous display of the chlorophyll in 
relation to the light-supply. In general they natur- 
ally take the form of a broad thin blade, protected 
as may be necessary against extremes of weather, and 
guarded against the obvious danger of being dried up 
by a thin waterproof covering or cuticle outside the 
epidermal layer of cells. In leaves we find the same 
beauty of mechanical construction as is seen in stems. 
The problem is again that of securing maximum eff- 
ciency with minimum expenditure of material. To 
give as great a surface as possible, the leaves are as 
broad and thin as is consistent with safety, the ques- 
tion of damage by wind being an important control- 
