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ig- 15 Section of potato-leaf in the tissues of which is the mycelium 

 of Pliytophtkora. The hypliae run between the cells, and send through 

 the stomata (a, c, d) the aerial branches which bear the conidia, b. /, 

 one of the peculiar hairs of the underside of the leaf. The dark parts 

 of the tissue of the leaf show where cells are dying from the effects of 

 the parasite. Highly magnified. The normally upper surface of the 

 leaf is here turned downwards. Marshall Ward. 



