While stems, such as the Big Trees or the giant cactus, may be among the largest of nature’s creations they may be also the smallest, as the duckweed that floats on ponds is the tiniest of all flowering plants and its flat expanded surface is wholly stem. Figure 12 on this page better illustrates this strange modification of a stem than words could do.
From what has been read it will be seen that stems are not “just stems”—they are among nature’s most ingenious devices to secure the survival of the plant. Whether buried in the ground, and producing, almost by stealth, buds that develop into mature plants, or thrusting leaves to the utmost limits of their reach, or climbing by an intricately varied mechanism, or changing their character to suit desert conditions, or floating on the water—it matters not. Each modification of form or use secures to the individual plant its chances to survive; and in most cases its only chance, as anyone may see by the sudden death which follows a series of changes which prevents a stem from performing its proper tasks.