I cut open a Kanza pecan today to check on the kernel filling process (photo above). What I found was a layer of white kernel tissue just inside the seed coat, then a layer of translucent gel-like material just inside the white layer. What I actually captured on film was the kernel filling process.
The process of kernel deposition starts on the inner surface of the seed coat and then works inwards toward the center of each kernel half. New kernel tissue starts off in a gel-like form. Then, as addition carbohydrates flow into the kernel, that gel become more solid and white. As the season progresses, kernel tissue will be packed so tightly inside the shell that the kernel will actually compact the center wall partition and all the packing material found on the inside of the shell.
Some folks just eat pecan kernels and never consider how those golden kernels were made. However, I find watching the process of kernel filling fascinating.