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COO Rae 5 tructural and Physiological Botany, © * 
in rushes and sedges, on the contrary, closed or entire. 
The split sheath of many Umbelliferze is inflated ; while the 
closed sheath of the knot-grass, Polygonum, does not bear 
the leaf at its upper end, but on its back, and is in this case 
called an ochrea. 
The fetzole is not always present ; and leaves are hence 
distinguished into petzolare or stalked, and sessz/e. It is often 
Sa Fic. 143.—Leaf of Acacta melanoxylon, showing phyllodes, a 0. 
connected with the stem, rarely with the sheath, by a pecu- 
liar more or less swollen articulation. If this articulation 
is large, and a portion of it remains attached to the stem 
after the fail of the leaf, as in the spruce-fir, the portion, that 
thus remains is called a pulvinus. After the fall of the leaf, 
the spot to which it was attached is indicated by a scar or 
cicatrix. The petiole may be cylindrical, semicylindrical,. 
channeled, or flat, and is sometimes winged, or provided 
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