Endospermic seeds are those which seed enosperm is located outside of cotyledons and cotyledons are tiny or leafy, ex: castor bean seeds. Cotyledon seeds or non-endospermic seeds are those which seed endosperm is absorbed by cotyledons and hence cotyledons are swollen, ex: bean seed.

Endosperm and cotyledons are same part, before germination that part having nutritive tissue after entering the water molecule, metabolic process has to starting become Endosperm colour is changing into green colour,  now it is called cotyledons.  

Before germination - Endosperm

After germination - cotyledons

Endospermic seeds are those which seed enosperm is located outside of cotyledons and cotyledons are tiny or leafy, ex: castor bean seeds. Cotyledon seeds or non-endospermic seeds are those which seed endosperm is absorbed by cotyledons and hence cotyledons are swollen, ex: bean seed.

Kindly see the following link it may help

https://lh5.googleusercontent.com/proxy/lP1G9OE6PYF6Np-jTLsFzCponBFVhC_BI3lfJ_h8MWvvcGYS8iJVurH8Ov4V0pNyq03oekOjdMrCKTtROe4gtJwD=w448-h329-nc

thank a lot.

endosperm seed and cotyledon seed are different terms. endosperm seed is referring to seed like that of maize- monoecious plants,while that of cotyledon is referring to cowpea- leguminous seed.

ok but whats the difference between these seed Structurally?

Endospermic Seeds

Endospermic seeds are those that have an endosperm in the mature seed. It is fleshy, oily, surrounds the embryo, and functions as the sole food storage organ. Inside the seed coat, a thin and papery cotyledon is present. Monocot plants have endospermic seeds.

Non-endospermic Seeds

Non-endospermic seeds do not have an endosperm in the mature seed. The cotyledons are thick and fleshy, and function as the sole food storage organs. Dicot plants have non-endospermic seeds.

thanks to all

Not as clear and as succinct as I was expecting to understand the differences between endosperm and cotyledon. Thank you all.

Endosperm is a dead tissue with 3n cromossomes; generally the cell are the parenquimatic ones; it is part of maize seeds, but soybean has two lines of parenquimatic cells attached to the tegument and these cells are never is seen in the tetrazolium test because both are eliminate in the moment of the test. Cotyledons has 2n cromossomes and it is a live tissue, where dehydrogenases enzymes color the trifenil tetrazolium of red using an oxi-redox chemical  reaction.

Please, access Frontiers in Plant Science July 2014 because it  has update open access papers about this subject.

Walter