The mature seeds of plants such as gram and peas possess no endosperm, because

1.  these plants are not angiosperms

2.  there is no double fertilisation in them

3.  endosperm is not formed in them

4.  endosperm gets used up by the developing embryo during seed development

 

 

Endosperm is a nourishing tissue of seed which provide nourishment to the developing embryo either before or after germination. In gram and peas, the endosperm gets used up at the time of development of seed. So, seed is non-endospermic, i.e., endosperm is not present in the mature seed.