The smallest seed I have ever seen has come from or local native terrestrial orchids lady slippers and showy orchis. the seed is the size of a period mark. To cultivate these plants from sed one must sow them in culture on a complete TC medium with vitamins and organics in the form of amino acids. In nature- after seed germination- it is common for these plants to live in the soil with out producing leaves for a number of years after gemination.