. The Botrytis blight of tulips ... Botrytis; Tulips. 354 Edwin F. Hopkins. Fig. 4^5. penetration of leaf TISSUE. X 277 Transverse section of epidermis. (Camera-lucida drawing) between epidermal cells (figs. 46, 47). The germ tubes have not been observed to penetrate directly through epidermal cells. It has been noted that penetration more often occurs where the conidia are more numerous. Probably this is because of the greater enzymatic action, which hydrolyzes the cuticular substance. The mycelium in the leaf, like that in the bulb, is both inter- and intracellular. This is shown in figures
. The Botrytis blight of tulips ... Botrytis; Tulips. 354 Edwin F. Hopkins. Fig. 4^5. penetration of leaf TISSUE. X 277 Transverse section of epidermis. (Camera-lucida drawing) between epidermal cells (figs. 46, 47). The germ tubes have not been observed to penetrate directly through epidermal cells. It has been noted that penetration more often occurs where the conidia are more numerous. Probably this is because of the greater enzymatic action, which hydrolyzes the cuticular substance. The mycelium in the leaf, like that in the bulb, is both inter- and intracellular. This is shown in figures 48 and 49. After the fungus has developed for a time in the leaf tissue, a collapse of the cells results and causes the leaf to become much thinner in the diseased area. Here also, where the mycelium is still intercel- lular, the cells are not killed. There is injury caused in advance of the mycelium. This indicates the excretion of toxic or enzymatic substances by the pathogene. The writer thinks that the injury caused in this disease is not due to oxalic acid. Some experiments were made to determine what the nature of the injury from oxalic acid would be. Several plants were injected hypodermically with solutions of oxalic acid of various concentra- tions, and lesions were produced which strikingly resembled those caused by a fungus. Further- more, microscopical examination indicated that no fungus had been accidentally introduced. However, the concentrations were necessarily higher than those produced by fungi in cul- ture. The work of Brown (1915) seems to show that neither oxa- lates nor oxalic acid take part Fig. 47. penetration of leaf tissue, x 277 in the toxicity of B. Cinerea, but Surface view. (Camera-lucida drawing). Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Hopkins, Edwin Fraser, 1891- [fr
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Keywords: ., bookcentury1900, bookdecade1920, booksubjecttulips, bookyear1921
