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A TEXTBOOK OF THEORETICAL BOTANY 



D 



E ^ 



p,(, 26, —Rhytisma acerinum. A, Epidermis and palisade of leaf at early stage of infection. 

 ■ B Early stage in formation of acervulus, rupture of epidermal %^-aIIs and deposition 

 of black substance. C, Later stage showing differentiation of basal plectenchyma and 

 vertical conidiophores. D, Early stage in apothecial formation showing formation ot 

 upper and lower plectenchyma. E, Later stage of apothecium showing increased 

 formation of roof plectenchyma. F, Apothecium with paraphyses among which the 

 ascogonia are formed. {After Jones.) 



