COUTANT: WOOD PERIDERM IN CERTAIN CACTI 361 
Within is (2) the layer of discolored cells whose protoplasmic 
contents appears to have degenerated and the walls of which are 
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Fic. 3. Diagrammatic cross section through a thirty-one-day-old wound of an 
Opuntia versicolor plant, X 24. a, old tissue, bordering upon wound surface; very 
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m; ¢, first 
fem; e, suberized thin-walled cells, produced by first 
adios teaalencaes f, young vascular bundles produced by second wound-meristem; 
g, “ph erm” tissue, produced by first and second wound-meristems, the cells 
being cellulose-walled, and containing small amounts of stored starch and oxalate 
crystals; &, old vascular bundles. 
almost completely lignified. Bordering upon them is (3) the 
suberized phellem tissue, averaging four or five cells deep, below 
