technicly, grangers dun have sex
thats why the "J!OO ♂+♀=??"
They spawn fertilized. Their eggs are the stuff that provide conception and the resulting feutus with it's nutrients while it grows.
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How can you be confused by my so detailed explanation? Ok, ill explain more clearly.
Grangers, at birth, would already have undergone fertilization, which occurs as the feutus (of the granger) is growing, through meiosis. The spermatozoa, which comes from (most likely) the overmind, travel through the network of creep, in glands, to the eggs, where they meet the ovum(s) in the egg itself. Once conception and fertilization occur, the granger grows into a mature granger. Once this happens, the egg 'gives birth' to the granger, allowing it to build more biological structures for it's species.
Dretch, on the other hand, follow the first few stages, until the point of fertilization, in which case, due to unknown reasons, forces the feutus to grow into a dretch, rather than grangers. The cell structure during the fetal stage somehow rearranges to produce a protein called Dresca 1-65, which is known to give dretch their brown/golden yellow colour. With grangers, the cell structure produces another protein, called Gran 6LG, which somehow allows grangers to be able to build other structures, due to some unknown telemagnetic force. This protein is also responsible for the leaf green colour of grangers.