Orchid leaf. Light micrograph (LM) of a transverse section through the leaf (pinna) of an orchid plant. The Orchidaceae are a diverse and widespread family of flowering plants, with blooms that are often colourful and fragrant, commonly known as the orchid family. Along with the Asteraceae, they are one of the two largest families of flowering plants. Like most monocots, orchids generally have simple leaves with parallel veins. The spongy mesophyll has air spaces for gas exchange and produces carbohydrates by photosynthesis. The upper and lower cuticle protect the leaf from water, sealing water inside and preventing excess rainwater from entering. The upper and lower epidermis produce the cuticle and protect the leaf from herbivores and parasites. The xylem transports water into the leaf while the phloem begins the sugar transport down to the roots. Magnification: x15 at 10 cm wide.