Fungi, Ascomycetes, Ustilaginales, Uredinales . s able to recognize an antheridium and oogonium and theformation of an ascus or asci from the latter. These and several subsequentinvestigations have rendered the reproductive processes in the Erysiphaceaebetter known than perhaps in any other group of fungi. Spliaerotlieca Humuli* occurs on a variety of common plants, on thecultivated strawberry, where it is responsible for strawberry mildew,and especially on the hop. On the latter it is widely distributed inautumn, and, if the female inflorescences are infected, may do considerabledamage. The m
Fungi, Ascomycetes, Ustilaginales, Uredinales . s able to recognize an antheridium and oogonium and theformation of an ascus or asci from the latter. These and several subsequentinvestigations have rendered the reproductive processes in the Erysiphaceaebetter known than perhaps in any other group of fungi. Spliaerotlieca Humuli* occurs on a variety of common plants, on thecultivated strawberry, where it is responsible for strawberry mildew,and especially on the hop. On the latter it is widely distributed inautumn, and, if the female inflorescences are infected, may do considerabledamage. The male and female organs arise as lateral branches from the mycelium,and project at right angles to the infected surface; they are borne on dif-ferent hyphae, but there is no evidence that these are derived from distinctmycelia. The oogonium, when fully grown, is an oval, uninucleate structuretwo or three times the size of an ordinary vegetative cell; it is cut off fromthe parent hyphae and a stalk cell may be differentiated below it (fig. 41 a).. Fig. 41. Sphaerotheca Humuli (DC.) Burr.; a. young oogonium and antheridium ; b. entrance of malenucleus; c. male and female nuclei in oogonium; d. fertilization; e. fusion nucleus; f. nucleiproduced by first division of fusion nucleus; g. young perithecium with binucleate ascogenouscell; x 1360; after Blackman and Fraser. 1 S. Humuli (DC.) Burr. = 5. Castagnei Lev. Ill] ERYSIPHALES The antheridial branch is much narrower; it applies itself to the side of the oogonium and when first cut off contains a single nucleus (tig. 41 <r).It is clearly differentiated from the hyphae of the sheath not only by itsform and behaviour but by its much earlier appearance and definite relationto the oogonium. Its nucleus soon divides; one of the daughter nucleipasses to the apex of the branch and a wall is formed cutting off the uni-nucleate antheridium. The oogonial nucleus is rather larger than those ofthe vegetative cells, the antheridial nucleus de
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectfungi, bookyear1922
