Water is fed in continuously from the bottom and kept at a constant level. Heating may be provided. For diagram see Figure 1. They are called clones.
Monocotyledons have one and dicotyledons have two cotyledons in each seed.
Overcrowding of seedlings and poor drainage of seed mix are common causes. Destroy seedlings as soon as detected. A shaded area or a shady, wind-protected position in the garden is used to acclimatise the young plants for a week or two, then a further three days of exposed hardening off is recommended prior to planting out. Certain synthetic hormones can be applied to cuttings to encourage quick root formation. They are particularly useful for slow rooting species.