. Diseases of plants induced by cryptogamic parasites; introduction to the study of pathogenic Fungi, slime-Fungi, bacteria, & Algae. Plant diseases; Parasitic plants; Fungi. CUCURBITARIA. 207 an acute beaked pore. Where the bark has been lost, a good lens may distinguish the spherical or ovoid dark-coloured perithecia. On the finer twigs the whole bark is often perforated by numerous tiny pycnidia, hardly distinguishable with the naked eye. If these various forms of fructification be submitted to microscopic examination, sections through the yellow pustule^ will show them to have that col
. Diseases of plants induced by cryptogamic parasites; introduction to the study of pathogenic Fungi, slime-Fungi, bacteria, & Algae. Plant diseases; Parasitic plants; Fungi. CUCURBITARIA. 207 an acute beaked pore. Where the bark has been lost, a good lens may distinguish the spherical or ovoid dark-coloured perithecia. On the finer twigs the whole bark is often perforated by numerous tiny pycnidia, hardly distinguishable with the naked eye. If these various forms of fructification be submitted to microscopic examination, sections through the yellow pustule^ will show them to have that colour, because the transparent periderm has become loosened from the rest of the bark; underneath the corky layers will be found a red stroma of pseudo- parenchymatous hyphal tissue. This stroma by its growth causes a gradual rupture and loosening of the corky and other layers of the periderm; wherever this takes place, conidio- phores are developed, and give off numbers of tiny, hyaline, ovoid or cylindrical conidia. The stroma itself is somewhat spongy, and encloses numerous cavities which also become lined with conidiophores. At a later period the tissue enclosing these cavities may become dark coloured, so that structures similar to pycnidia are formed. In such cavities the red colour disappears, and the hyphae, coni- diophores, and conidia appear transparent. The real pycnidia appear later, and consist of a peridium of coarse pseudoparenchyma con- taining conidia similar to those just described (Fig. 99, a). From the openings of these pycnidia the conidia emerge as red tendrils, rising as much as one centimetre above the pore. Adjoining these forms of sporo'phore just described will be found others : unde- veloped perithecia with young asci ; dark- brown pycnidia with brownish-grey, multi- septate, compound conidia ; or similar pycnidia with unicellular spherical, brownish-grey conidia. Where the disease has made further j)rogress, the pustules. Fig. hljirnii. fiS.—Cacurbi
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Keywords: ., bookcentury1800, bookdecade1890, bookpublisherl, booksubjectfungi
