Text-book of botany, morphological and physiological . ctionof the SaprolegniecE proper presents two cases, according as the species is or is not provided with lateralbranches. In the first case prolongations of the antheridia traverse the wall of the oogonium, whichmay or may not have been previously perforated. Max Cornu has never seen spermatozoids pro-duced by the antheridium, which empties itself by an influx of its protoplasmic contents; the process R 2 244 TiiALLUfnrT±::s. (2) The Peronosporeas^ live in the interior of Phanerogams, the branches oftheir imicelhilar mycelium growing betwe
Text-book of botany, morphological and physiological . ctionof the SaprolegniecE proper presents two cases, according as the species is or is not provided with lateralbranches. In the first case prolongations of the antheridia traverse the wall of the oogonium, whichmay or may not have been previously perforated. Max Cornu has never seen spermatozoids pro-duced by the antheridium, which empties itself by an influx of its protoplasmic contents; the process R 2 244 TiiALLUfnrT±::s. (2) The Peronosporeas^ live in the interior of Phanerogams, the branches oftheir imicelhilar mycelium growing between the cells of the tissue from which theydraw their nourishment by peculiar organs of suction (Haustoria) (Fig. 168, A, h). Themycelium produces first of all asexual fertile branches which project above the surface;in Peronospora they protrude through the stomata and branch in an arborescentmanner; in Gystopus they are club-shaped (Fig. 168, B) and closely packed, forminga hymenium beneath the epidermis. The separated Conidia are in some species of. Fig. 169.—Cystopus candidtis. A mycelium with young oogonia ; B oogonium og with oosphere os and antheridium an;C ripe oogonium; Z> ripe oospore ; E,F,G formation of swarm-spores from oospores ; z endospore (after De Barj) (x 400). Peronospora simple spores, in others (as P. infestans), and in all species of Gystopus,they are not immediately capable of germination, but when in contact with water, as forinstance drops of dew or rain, develope several zoospores (Fig. i68, C, Z), -E, i^). Insome species cf Gystopus the terminal member of each row of conidia is capable of is in fact one of true conjugation. Where there are no lateral branches fertilisation would seem tobe required by means of antherozoids. Max Cornu believes that the supposed spermatozoids discoveredby Pringsheim really belong to an endophyte of the group ChytridinecB, which have often been iden-tified with organs of the plants they infest. He thinks it probable
Size: 1461px × 1711px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1870, booksubjectbotany, bookyear1875
