PLATE 29 



A. — End of a silk: p, pollen grains; v, fibro-vascular bundles; h, hairs. X 3$. 



B. — Tips of the hairs of the silk. It is on these hairs that most of the pollen grains 

 lodge. X 250. 



C. — Section of a pollen grain showing the germ pore and the relative size of the 

 vegetative and sperm nuclei. X 250. 



D. — Single hair of the silk, showing the general manner in which the pollen tube 

 penetrates the sheath cells of the fibro-vascular bundle of the silk: p, pollen grain; 

 h, hair; pt, pollen tube; sc, sheath cells of the fibro-vascular bundle. X 250. 



E. — Longitudinal section of a fibro-vascular btmdle of a silk, showing the position 

 of the pollen tube as it grows down the silk: sc, sheath cells; x, xylem elements; p, 

 parenchyma cells of the silk; pt, pollen tube, showing the enlarged tip. X 250. 



