Here's the same tree with pictures for the units. I'm not sure if it's much of an improvement, I didn't have room to put in more than their little profile pictures. Aside from the Flying Line Galleus because it's a pain!
Things to note are that just having a Training Grounds will let you upgrade Green Bats to Blackshadows. But to actually build Blackshadows as a unit, your city will need both the Training Grounds and a Bat Fort.
Likewise, you can upgrade a Flying Galleus to a Flying Line Galleus as long as you have the Military Academy. To build a Flying Line Galleus requires a city with an Air Dock and the Military Academy. Which means you need at least a Level 9 city to build them, making them the most time consuming unit to make from scratch. And they're bad.
