. Botany of the living plant. Botany; Plants. IRREGULAR NUTRITION 233 almost devoid of chlorophyll, are, like Monotropa and Sarcodes, obviously incapable of normal plant nutrition. The general view, which is not entirely satisfactory, is that during the course of evolution the plants have come to rely chiefly on organic food secured from the mycorrhizal fungus ; and this in turn derives its supply from the abundant humus of the soil which these plants inhabit. It is, however, probable that in the seedling stage all Orchids, green or sapro- phytic, are to some extent dependent on assistance der
. Botany of the living plant. Botany; Plants. IRREGULAR NUTRITION 233 almost devoid of chlorophyll, are, like Monotropa and Sarcodes, obviously incapable of normal plant nutrition. The general view, which is not entirely satisfactory, is that during the course of evolution the plants have come to rely chiefly on organic food secured from the mycorrhizal fungus ; and this in turn derives its supply from the abundant humus of the soil which these plants inhabit. It is, however, probable that in the seedling stage all Orchids, green or sapro- phytic, are to some extent dependent on assistance derived from the mycorrhizal fungus. Observation shows that in the presence of the fungus, infection of the Orchid seedling frequently occurs at a very early stage (Fig. 161). The difficulty of securing germination of Orchid seeds in horticultural practice is well known. Ex- periment has shown that usually Orchid seeds will not develop under sterile condi- tions. Inoculation with the fungus is fol- lowed by normal germination (Fig. 162). The explanation may be that the Orchid seed requires a stimulus before germination will take place ; the stimulating substance, and additional food, may be provided by the fungus. The nutritional aspect is supported by experiments which show that if Orchid seeds are provided with organic food such as sugars, normal development will proceed in the absence of the fungus. Both of these observations have been put to practical application in horticulture, and Orchid plants can be raised (a) by sowing seeds on special soil infected with the mycorrhizal fun- gus, or (b) by feeding the seedlings with organic materials. The. Fig. 160. Lower part of a plant of Neottia nidus-avis, showing the dense mass of roots springing from a central rhizome, which is concealed by the roots. s=scale-leaf. /=flower. r=root. ( x §.). Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and a
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Keywords: ., bookcentury1900, bookpublis, booksubjectbotany, booksubjectplants
