DR KEITH WHEELER / SCIENCE PHOTO LIBRARY DR KEITH WHEELER / SCIENCE PHOTO LIBRARY
Water fern spores. Light micrograph of a transverse section through a water fern (Salvinia natans), showing macrospores in a macrosporangia. The water fern produces spores of two kinds, large female ones and small male ones. Only the female spores (called megaspores, round, blue capsules, red inside) are seen here. These are released from their macrosporangia into water and then germinate and develop in several stages, resulting in an egg. The male spores go through a similar process, culminating in their fertilisation of an egg to form a new fern plant (sporophyte). Magnification: x37 when printed at 10 centimetres tall.
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