The Construction of the Plant out of Cells. 65 + 
of the stem or root is thus constantly increasing in thickness, 
as is the case in most woody Dicotyledons and Conifers. 
Closed bundles, on the contrary, such as are found in Cryp- 
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Fic. 93.—Transverse section through the fibrovascular bundles of the sugar-cane ; 
Hf parenchymatous cells of the xylem ; H/ wood-fibres ; g'* spiral vessels ; 2”° 
pitted vessels ; Bf bast-parenchyma; By bast-vessels or sieve-tubes ; B/ bast- 
fibres. (X 360.) 
togams, Monocotyledons, and a few Dicotyledons, can no | 
longer increase in thickness. The various forms of tissue 
in a mature fibrovascular bundle may be divided into two 
F 
