. Beginners' botany. Botany. Fig. 286. —Part of Gill of the Cul- tivated Mushroom. ir, trama tissue; j/i, hymenium; 5, basidium; sii sterigma; sp, spore. (Atkinson.) nection with which the spores are borne. These aerial parts are the only ones we ordinarily see, and which constitute the "mush- room" part (Fig. 131). Only asexual spores (ba- sidiospores) are produced, and on short stalks (basidia) (Fig. 286). In the puff- balls the spores are inclosed and constitute a large part of the "; In the mushrooms and toadstools they are borne on gills, and in the shelf fungi (
. Beginners' botany. Botany. Fig. 286. —Part of Gill of the Cul- tivated Mushroom. ir, trama tissue; j/i, hymenium; 5, basidium; sii sterigma; sp, spore. (Atkinson.) nection with which the spores are borne. These aerial parts are the only ones we ordinarily see, and which constitute the "mush- room" part (Fig. 131). Only asexual spores (ba- sidiospores) are produced, and on short stalks (basidia) (Fig. 286). In the puff- balls the spores are inclosed and constitute a large part of the "; In the mushrooms and toadstools they are borne on gills, and in the shelf fungi (Fig. 134) on the walls of minute pores of the underside. The my- celium of these shelf fungi frequently lives and grows for a long time concealed in the substratum before the visible fruit bodies are sent out. Practically all timber decay is caused by such growth, and the damage is largely done before the fruiting bodies appear. For other ac- counts of mushrooms, see Chap. XIV. Lichens Lichens are so common everywhere that the attention of the student is sure to be drawn to them. They grow on rocks, trunks of trees (Fig. 287), old fences, and on the earth. They are thin, usually gray ragged objects, ap- parently lifeless. Their study is too difficult for beginners, but a few words of explanation may be useful. Lichens were formerly supposed to be a distinct or separate division of plants. They are now known to be or- ganisms, each species of which is a con- stant association of a fungus and an alga. The thallus is ordinarily made up of fun- gous mycelium or tissue within which Fig. 287.^Lichen on an the imprisoned alga is definitely dis- Oak Trunk. (A species tributed. The result is a growth unlike cf Phvscia^ either component. This association of. 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 Bailey, L.
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