REMARKABLE EXAMPLES OF SPECIATION IN ASIATIC PLANTS

The nature, extent, and tempo of speciation differ from one plant group to another, and some noteworthy examples studied in Asiatic flowering plants are considered. In the Rubia cordifolia group, Himalayan plants have epigeous cotyledons, while all Japanese plants have hypogeous cotyledons; in both groups polyploidy seems to have occurred parallelly. The pollen pattern varies in some groups correlated with polyploidy, and an example is observed within a species ( Anemone hepatica ) or a genus ( Isopyrum , etc.). Representative examples in which polyploidy plays an important role in speciation are explained in such genera as Aucuba, Helwingia, Duchesnea, Agrimonia and Suaeda . Dysoploidy and amphiploidy are also important, and establishment of new basic numbers is occasionally found in closely allied species as exemplified in Lysimachia and Chrysosplenium , or even in one species, Chionographis japonica . As a striking example of an exceedingly polymorphous species which is considered to be undergoing speciation, the variations in Paris polyphylla are reviewed. On the contrary, Phryma leptostachya is not highly differentiated, although it occurs in two widely separated regions, and must be of very old origin.