. A textbook of botany for colleges and universities ... Botany. SAPROPHYTISM AND SYMBIOSIS 793 so that the mycelium often is continuous (figs. iio6, 1107); frequently also haustoria are present, and sometimes the internal hyphae are con- tinuous with the hyphae which ramify the soil. Root hairs commonly are scarce and are more or less filled with hyphae. Many root cells are free from fungi, including some of the outer cells as well as those of the vascular tract.^ Endotrophic fungi are as- sociated with the tuber-like gametophytes of Lycopodium and Botrychium (fig. 1108). Transitional forms b
. A textbook of botany for colleges and universities ... Botany. SAPROPHYTISM AND SYMBIOSIS 793 so that the mycelium often is continuous (figs. iio6, 1107); frequently also haustoria are present, and sometimes the internal hyphae are con- tinuous with the hyphae which ramify the soil. Root hairs commonly are scarce and are more or less filled with hyphae. Many root cells are free from fungi, including some of the outer cells as well as those of the vascular tract.^ Endotrophic fungi are as- sociated with the tuber-like gametophytes of Lycopodium and Botrychium (fig. 1108). Transitional forms between ectotrophic and endotrophic mycorhizas are not rare, being characteristic of the Ericaceae; in Monotropa,. Figs. 1106, 1107. â Endotrophic mycorhiza of orchid roots: 1106, a cross section through a part of a root of Aplectrum hyemale, showing dense clumps of fungal hyphae (/) in some of the larger cortical cells, several rows inside of the epidermis (e); f, root hairs; v, vas- cular tract; 1107, a single cortical cell from the root of Spiranthes cernua, showing fungal strands (/), cyto- plasm (c), and the nucleus («); 1106 considerably, and 1107 highly magnified. for example, hyphae from the fungal sheath invade and modify the epidermal layer (fig. 1105). Even ecto- trophic fungi may penetrate into the root, though in that event they commonly are intercellular rather than intra- cellular, as in most endotrophic forms. In some pines there are both ectotrophic and endotrophic mycorhizas, the relative develop- ment of the two kinds varying with the habitat. In some climb- ing plants (as Vanilla) the fungus is both ectotrophic and endo- trophic and is said to penetrate _ â A .â ii. u I . even the tissues of the supporting Fig. 1108. â A section through the gameto- r phyte of Botrychium, showing endotrophic plant as well as those of the liana, mycorhiza, the fungi inhabiting the ventral There is little doubt that the region; considerably magnified. â After coralloid a
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbotany, bookyear1910
