From what I have read, glosso seems to grow horizontally under strong light and vertically with less light ("reaching for the sun"?).
Here's one of the several links I found:
http://fins.actwin.com/aquatic-plant.../msg00387.html
But some have said that they have grown it horizontally under low light.
I do know that E. stellata grows taller under higher light. I can see that just 10 feet away.
But that's probably a different thing.
I'm glad for the chance to add to the confusion.
Bill