. Diseases of plants induced by cryptogamuc parasites; introduction to the study of pathogenic fungi, slime-fungi, bacteria, and algae. English ed. by William G. Smith. Plant diseases; Parasitic plants. 238 ASCOMYCETES. ripening in the spring of the fourth year. Or, again, a " casting" of brown one-year-old needles may take place in autunni. The disease is found everywhere, but in some parts { in the forests of Saxony ^), it is exceedingly common and very dangerous. The apothecia are developed as long, shining, black swellings on the two under surfaces of the quadrangular needles
. Diseases of plants induced by cryptogamuc parasites; introduction to the study of pathogenic fungi, slime-fungi, bacteria, and algae. English ed. by William G. Smith. Plant diseases; Parasitic plants. 238 ASCOMYCETES. ripening in the spring of the fourth year. Or, again, a " casting" of brown one-year-old needles may take place in autunni. The disease is found everywhere, but in some parts { in the forests of Saxony ^), it is exceedingly common and very dangerous. The apothecia are developed as long, shining, black swellings on the two under surfaces of the quadrangular needles (Fig. 121). The club-shaped asci emit thread-like spores with gelatinous coats. The ascospores produce a strong germ-tube, which grows inside the needles to an intercellular mycelium without haustoria. Browning and shrinkage of the cells of attacked needles soon follow. The myce- lium also penetrates into the cells of the epidermis, and develops there a coil of hyphae, which, under a black membranous cover, forms an apothecium containing paraphyses and club-shaped asci (Fig. 1'2'2). When ripe, the apothecia rupture the overlying epidermis. Little black pycnidia (spermogonia) may also occur on diseased needles.^ On needles which have been prematurely cast, only little spherical apothecial knobs will be found. According to Hartig, the effects of this fungus on the cells of attacked needles is very interesting. If the disease of the needles appears in autumn, the cells, which at this time are void of starch, become brown and die. If the disease attacks in May, when the needles are rich in starch, their death ensues soon, but the starch only disappears gradually from October onwards, as it is used up by the fungus-hyphae. If the disease appears in spring, when starch-storage is just beginning, the cells already attacked become quite full of starch, whereas the other cells of the same needle remain Fig. 123. —Lophodermium macrosporum on Spnice. Germinated ascospores; some
Size: 864px × 2892px
Photo credit: © Paul Fearn / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, booksubjectparasit, bookyear1897
