WOOD, CAMBIUM, AND BAST 19 
obtained from these vessels, and opium also from the seed 
vessels of a kind of Poppy. 
In the higher plants the long tubes, whose formation 
we explained, together with many elongated cells, are 
collected into “bundles,” called specially jibro-vascular 
bundles, and a typical bundle is composed of three 
elements—wood, cambium, and bast—arranged thus :— 
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DIAGRAM OF BUNDLE. 
b. Bast. ec. Cambium, w. Wood. 
Bast may be simply described as the fibrous inner 
bark, while cambium is the layer of cellular tissue in 
which the growth of the bark has its origin. Before 
we go any further, let us clear up one point. These 
bundles exist in all flowering plants, say, for example, 
in the daisy and the buttercup. Yet you will say that 
there is certainly no wood at all in such plants. That 
is true in a way, but the ordinary wood, as we know it 
in the trunk of a tree or in a plant, is really made of 
the woody part of innumerable bundles, tightly packed 
together as the tree grows. In every leaf of a tree 
there is a certain amount of wood material, but it does 
not become conspicuous until we have a large number 
altogether. 
One thing always to be kept in mind is that what 
