Stem plants extending a single stem, floating or planted

Stem plants are the plants that tend to grow from a single growing point, forming one elongating stem. These are the floating stems, which are sometimes called "bunch plants," maybe, I like to think, because you must not plant them in a bunch. When you get stem plants home, whether you've carried them in a plastic bag from your LFS or receive them in the mail, they will have travelled wet, but not in water. Water has been omitted not because the LFS salesperson was too thoughtless to include it, or your e-source was too cheap to pay the freight for it. Water would only slosh around in transit and break stems and bruise leaves.
 
Stem plants float because of the oxygen and other atmospheric gases trapped in their aerenchyma, the tubular internal channels that penetrate deep into the structure of their leaves and the fine roots that tend to spring from the nodes along the stem, which also produce leaves. Through their arenchyma, water plants permit the diffusion of carbon dioxide and oxygen throughout the floating plant.
 
 
A tip about stem plants. You will want to float the stem plants in water before you plant them, and I strongly recommend that you first cut an inch off the base of the stem, holding it under water as you snip. Why? Travelling damp, the plant will have drawn a little air into its vascular bundles, and you don't want an air bubble to interfere with the circulation of water and nutrients along the stem. Besides, where the stems have been clipped or banded together, their stems have been bruised and squashed; they will decay in water.  If you think this is an unnecessary precaution, try a little experiment yourself: clip the stem ends of half your new stem plants under water, and judge whether they don't recover just a little faster than the uncut ones.