. A textbook of botany for colleges and universities ... Botany. 8l2 ECOLOGY Various features of structure or habit facilitate spore dispersal. As previously noted, many fungi bear spores externally, so that they are readily blown away as soon as they are abstricted. In the fleshy fungi, the spore-containing organs often are borne on conspicuous apogeo- tropic stipes, which thus elevate the spores into a good position for wind dispersal (figs. 1078, 2, 197). In many of these forms the spores are dis- charged from the gills, after which they drop into positions where they may be wafted oS by ai
. A textbook of botany for colleges and universities ... Botany. 8l2 ECOLOGY Various features of structure or habit facilitate spore dispersal. As previously noted, many fungi bear spores externally, so that they are readily blown away as soon as they are abstricted. In the fleshy fungi, the spore-containing organs often are borne on conspicuous apogeo- tropic stipes, which thus elevate the spores into a good position for wind dispersal (figs. 1078, 2, 197). In many of these forms the spores are dis- charged from the gills, after which they drop into positions where they may be wafted oS by air currents. In Coprinus (figs. 198, 199), which has a cylindrical fruit body, the spores mature first in the lower part, which then curves outward, and hence does not hinder the dispersal of those which ripen later. Where spores are borne within sporangia or similar organs, there often are no special features which facilitate spore removal, it being necessary for the enveloping organs to rot away before the spores can be dispersed. In some cases there is definite dehis- cence, as in Geaster, where the sporan- gial wall (peridium) has two layers, of which the outer splits into star- shaped segments (whence the com- mon name, earth star), while the in- ner has an apical opening (fig. 1124); in the related puffballs the outer layer breaks irregularly. In Geaster the hyphae are arranged at right angles to the surface in the inner { upper when open) part of the ray and parallel to the surface in the outer part. Hence in moist weather the inner part absorbs the more water and the rays open (fig. 1124), while they close in dry weather (fig. 1123), since the inner part loses the more water. This hygroscopic mechanism has been thought to facilitate spore dispersal; the dry closed structure is bowled along by the wind like a tumbleweed, and the rain washes out spores from the opened structure. In a few fungi, spores are scattered by agents other than wind. In Pilobolus (fig. 630) the
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbotany, bookyear1910
