The purpose of the morph tree is to illustrate the way that different morphs are related to each other. The tree originates with normal in the center. By following the lines outward, it is possible to "construct" a morph.
The rectangles represent morphs that are based on on/off genes. The dashed rectangles are instances of morphed corns that result from being heterozygous for two different mutant alleles at the same locus.
Note that two-locus combinations are not included in the tree, only genetic morphs based on genes at a single locus. Including combinations would make the map much more complex, and nearly impossible to read because branches would all interconnect to every other branch, like a spider web. This map is just the first "layer" of the world of corn morph possibilities. The "Genetic Morphs" chapters in the CMGs show many of the two-gene combinations.
The ovals represent morphs that are created through selective breeding. Smaller ovals represent secondary selective breeding. For example, with candycanes, which are selectively bred, there are projects selecting among candycanes for the ones with orange saddles.
As time passes and new generations are hatched, the tree will gain more branches as new genes are discovered, and as new selectively bred variations are created within each genetic morph type.