Acotyledon is used to refer to seed plants or spermatophytes that lack cotyledons, such as orchids and dodder. Orchid seeds are tiny with underdeveloped embryos. They depend on mycorrhizal fungi for their early nutrition so are myco-heterotrophs at that stage. Although some authors, especially in the 19th century and earlier, use the word acotyled...[mite] Acotyledon is a genus of mites in the family Acaridae. ...
• (n.) A plant which has no cotyledons, as the dodder and all flowerless plants.
A·cot`y·le'don (#; 277) noun [ Greek 
acotyledon Any plant without seed leaves.
a plant without cotyledons, therefore one belonging to a group lower than the seed plants.