1. In the successive developmental stages of Arisaema seedlings there are gradual transitional forms from small, usually simple or trifoliate leaves to large, trifoliate, pedate, or radiate compound leaves of adult plants (table 1 and fig. 3). 2. There is a significant correlation between (a) the shape of plumule leaf and (b) the morphology of adult leaf. 3. In each phyletic line, the types found in adult leaves seem to have evolved to get additional developmental stage (hypermorphosis) from groups with a few leaflets (3-5, plumule lamina simple) to groups with many leaflets (over 5, plumule lamina compound). 4. From these facts it is concluded : (a) the groups having simple plumule leaves consists of the primitive members of different phyla, (b) the species having compound plumule leaves are the highly specialized ones in this genus, (c) the type with cataphylle plumule (A. thunbergii group) is also in the specialized stage, (d) the radiate-group differs distinctly from the pedate-group.
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