Orchid seed. Coloured scanning electron micrograph (SEM) of a seed from a common twayblade (Listera ovata) orchid. Due to their small size, the seeds of orchids lack the endosperm (nutrient tissue) necessary for successful germination. Orchids are therefore dependent on a symbiotic relationship with fungi whereby the embryo's germination is initiated by the penetration of fungal hyphae into the seed. The embryo gains nutrients by digesting part of the fungal body and excretions from the fungus. Once the seedling is capable of photosynthesis, this takes over the supply of plant nutrients. Magnification: x113, when printed 10 centimetres wide.