The development of leaves of three ferns has been morphologically observed. In
Woodwardia orientalis, the leaves of the first year plant are simple and one lobed, while the second year leaves of the same individual plant show more complex forms being simple pinnate. In the next year the plant becomes to have more complex leaves showing more leaflets than the previous year leaves. Thus, in the final developmental stage the leaves show the complete pinnate forms.
In
Ceratopteris thalictroides and
Onoclea sensibilis, the change of leaf forms from simple to complex is observed in the first year in one and the same individual. The leaves appearing first are simple, while the subsequent ones show gradually more complex forms.
The present results of observation in the ferns may give data to the view: the change of leaf forms between different developmental stages may be considered that the telomes of young leaves are connected into a simple form, while those of more advanced leaves are separated to form complete pinnate forms.
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