. The fungi which cause plant disease . Plant diseases; Fungi. THE FUNGI WHICH CAUSE PLANT DISEASE 173 This binucleate cell after fusion of its nuclei develops into the one ascus characteristic of the genus. The ascus nucleus by- division gives rise to the spore nuclei and the spores are cut out of the periplasm by reflexion of the astral rays. In Erysiphe** the oogonium and antheridium arise in a very similar way, the oogonium being somewhat curved. Feri;ilization is also similar consisting of the union of two gametic nuclei. After fertilization the oospore nucleus divides and the oogonium de
. The fungi which cause plant disease . Plant diseases; Fungi. THE FUNGI WHICH CAUSE PLANT DISEASE 173 This binucleate cell after fusion of its nuclei develops into the one ascus characteristic of the genus. The ascus nucleus by- division gives rise to the spore nuclei and the spores are cut out of the periplasm by reflexion of the astral rays. In Erysiphe** the oogonium and antheridium arise in a very similar way, the oogonium being somewhat curved. Feri;ilization is also similar consisting of the union of two gametic nuclei. After fertilization the oospore nucleus divides and the oogonium de- velops into a short bent tube, which contains from five to eight nuclei. Septa now appear cut- ting off cells, some uninucleate, some with two or more nuclei. The ascogenous hyphae develop a knot and soon divide into two or three cells each and give rise to the asci which are in the beginning binucleate. T T>i. II â Si ii_ F'"- 125.âPhyllactinia, male and female In fnyliactmia °* the OOgO- branches; uninucleate oogonium and nium, antheridium and fertili- "â ^theridium. After Harper. zations are as in Erysiphe, though the oogonium may be quite curved so as to make almost a complete turn around the anther- idium. Fig. 125. After fertilization the antheridium degenerates and enveloping protective hyphae arise both from the oogonium and the antheridium stalk cells. The oogonium becomes three to five nucleate and develops to a row of cells of which the penultinate cell has more than one nucleus. The ascigerous hyphae arise from this binu- cleate cell, perhaps also from other cells of the series, become septate and form the asci either terminally, laterally or inter- calary. The young ascus is binucleate, fusion follows and the spores develop as in the preceding genera. The family contains, according to Salmon, forty-nine species and eleven varieties, according to Saccardo more than one hun- dred species. These are parasitic on some one thousand five hundred
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectfungi, bookyear1913
