. Elementary botany . 188 MORPHOLOGY. Curious as it may seem, these are the leaves of the horsetail. The stem, if we examine it farther, will be seen to possess numer- ous ridges which extend lengthwise and which alternate with furrows. Farther, the ridges of one node alternate with those of the internode both above and below. Likewise the leaves of one node alternate with those of the nodes both above and below. 381. Sporangia.—The end of this fertile shoot we see pos- sesses a cylindrical to conic enlargement. This is the fertile spike, and we note that its surface is marked off into regular
. Elementary botany . 188 MORPHOLOGY. Curious as it may seem, these are the leaves of the horsetail. The stem, if we examine it farther, will be seen to possess numer- ous ridges which extend lengthwise and which alternate with furrows. Farther, the ridges of one node alternate with those of the internode both above and below. Likewise the leaves of one node alternate with those of the nodes both above and below. 381. Sporangia.—The end of this fertile shoot we see pos- sesses a cylindrical to conic enlargement. This is the fertile spike, and we note that its surface is marked off into regular areas if the spores have not yet been disseminated. If we dissect off a few of these por- tions of the fertile spike, and examine one of them with a low magnifying power, it will appear like the fig. 234. We see here that the angular area is a Fig. 234. disk-shaped body, with a stalk attached to its inner phyficr/equfsSum8111*^06? aRd with several long sacs projecting from inges^Xngfa°on its inner face parallel with the stalk and surrounding the same. These elongated sacs are the sporangia, and the disk which bears them, together with the stalk which attaches it to the stem axis, is the sporophyil, and thus belongs to the leaf series. These sporophylls are borne in close whorls on the axis. 382. Spores.—When the spores are ripe the tissue of the sporangium becomes dry, and it cracks open and the spores fall out. If we look at fig. 235 we will see that the spore is covered with a very singular coil which lies close to the wall. When the spore dries this uncoils and thus rolls the spore about. Merely breathing upon these spores is sufficient to make them perform very curious evolutions by the twisting of these four coils which are attached to one place of the wall. They are formed by the splitting up of an outer wall of the spore. 383. Sterile shoot of the common horsetail.—When the spores are ripe they are soon scattered, and then the fertile shoot dies down. Soon afterw
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