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PLATE 30 



A. — Cross section of a silk near its base, showing the position of the fibro- vascular 

 btindles. X 220. 



B. — Cross section of a fibro-vascular bundle of the silk: x, xylem elements; sc, 

 sheath cells; pt, pollen tube. X 650. 



C. — Longitudinal section through the sheath cells of the fibro-vascular bundles: 

 sc, sheath cells; pc, parenchyma cells of the silk. It is between the sheath cells that 

 the pollen tube works its way down the silk. X 650. 



