Noland, Lowell E. (ed.) / Transactions of the Wisconsin Academy of Sciences, Arts and Letters
volume XXVI (1931)
Wentzel, Erna A.
Morphological studies of Erysiphe aggregata on Alnus incana, pp. -Plate IV ff. PDF (4.9 MB)
MORPHOLOGICAL STUDIES OF ERYSIPHEAGGREGATA ON ALNUS INCANA ERNA A. WENTZEL The powdery mildews offer especially favorable material for the study of the development of the perithecium. The following study was undertaken for the purpose of extending our knowledge of the group by an account of the development of the ascocarp and spore formation in the genus Erysiphe. REVIEW OF LITERATURE The structure of the ascocarp and the stages in its development have been fairly well understood since the time of De Bary (1863) and the main points of his conclusions have been many times confirmed. In his investigation of Sphaerotheca castagnei De Bary (1863) found that at the crossing point of two hyphae, or at the place where two neighboring hyphae touch, each hypha develops a small upright branch which is soon cut off by a septum from the parent hypha. One of these branches swells to an oval-oblong shape and becomes the oogonium. The other lengthens slightly and applies itself closely to the side of the oogonium, curving above itso that its end lies on the apex. The upper part is then cut off by a septum and forms the antheridium. De Bary observed no breaking down of the wall between the antheridium and oogonium and so supposed that no con-. jugation took place; nevertheless he considered that these organs represented a true sexual apparatus and that the perithecium subsequently formed was to be regarded as the result of a sexual act. This last conclusion has been verified by the works of Harper and others. Harper (1895) described the sexual apparatus for Sphaerotheca castagnei, Phyllactinia corylea, Erysiphe communis, and E. cichoracearum, and found them to arise in general in the same manner. He observed that the sexual apparatus is formed where two hyphae cross or lie close beside each other, thus the oogonium and antheridium arise as lateral branches from separate hyphae. , ,
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