. The fungi which cause plant disease . Plant diseases; Fungi. 330 THE FUNGI WHICH CAUSE PLANT DISEASE aecia are on pines (Peridermium), while the other stages are on dicotyledons. In the Gymnosporangiums the pycnial and secial stages are on Rosacese; the telial on Juniperus and its kin. While a few general rules can be worked out concerning host relations there are many exceptions and to know one stage of a heteroecious rust generally gives little or no clue to what its complementary host may be. The mycelium of the rusts is usually intercellular and local though in a few instances it is exte
. The fungi which cause plant disease . Plant diseases; Fungi. 330 THE FUNGI WHICH CAUSE PLANT DISEASE aecia are on pines (Peridermium), while the other stages are on dicotyledons. In the Gymnosporangiums the pycnial and secial stages are on Rosacese; the telial on Juniperus and its kin. While a few general rules can be worked out concerning host relations there are many exceptions and to know one stage of a heteroecious rust generally gives little or no clue to what its complementary host may be. The mycelium of the rusts is usually intercellular and local though in a few instances it is extensive and even perennial in the host. It is abundantly branched, closely septate, gives off haustoria and usually bears numerous oil drops which lend a yellow or orange color. Irritation by the mycelium often induces marked hypertrophy or even witches' brooms or other deformation of the host. Hy- pertrophy is most common with the aecia but may result from the telia as well, as is conspicu- ously shown in the genus Gymnospor- angium. In some instances the whole habit of the host plant is altered by the presence of the mycelium so as to render it almost tm- recognizable, e. g., the secium of Uro- Fio. 243.—Cross-section, showing infection from spore mtrnoc evn V,-, of P. asparagi. After Smith. myces piSl On iliU- phorbia. The host cells are seldom killed by the mycelium, which ab- stracts its food supply from the carbohydrates and other nutrients of the cell sap without direct injury to the protoplasm, though ultimately there is serious effect upon both growth of the host and its seed production. ;* ISO. Dangeard^i^ and Sappin-Trouffy"" showed that the mycelial cells of the rusts are binucleate, a condi- tion which begins just below the aecium. The origin and signifi- cance of this condition is of much Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability -
Size: 1807px × 1383px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, booksubjectfungi, bookyear1913
