THE VEGETATIVE ORGANS OF PLANTS. 271 
of the bast or inner bark of our common trees; those 
nearest the centre of the stem, c, are wood-cells. In the 
maize stem, bast and wood-cells are quite alike, and 
are distinguished only by their position. In other plants, 
they are often unlike as regards length, thickness, and_pli- 
ability, though still, for the most part, similar in form. 
Among the wood-cells we observe a number of ducis, d, 
e, f, and between these and the bast-cells is a delicate and 
transparent tissue, g, which is the cambiwm—in which all 
the growth of the bundle goes on until it is complete. On 
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ae 
aa (a 
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either hand is seen a remarkably large duct, 5, b, while the 
residue of the bundle is composed of long and rather 
thick-walled wood-cells. 
Our understanding of these parts will be greatly aided 
by a study of fig. 49, which represents a section made 
vertically through the bundle from c¢ to h, cutting the va- 
rious tissues and revealing more of their structure. In this 
the letters refer to the same parts as in ‘the former cut: 
a, a, is the cell-tissue, enveloping the vascular bundle; 
the cells are observed to be much longer than wide, but 
are separated from each other at the ends as well as sides 
Fig. 49, 
