Bauhinia variegata. PURPLE ORCHID TREE. India, Sri Lanka, China
LEGUMINOSAE or FABACEAE (Pea family)
Two specimens can be seen at Nos. 24A and 25A Rains Houses, where they are tucked into secluded corners and are evidently thriving, judging by their substantial size and prolific fruiting. They are seen only occasionally in the Bay Area, being more suited to Southern California. The interesting, edible leaves are 4 or 5 inches across, and indented at both base and apex, somewhat resembling a butterfly's wings. This geometry facilitates the closing of the leaves. The large flowers come in various tones of lavender and the tough seed pods, up to 6 inches long, contain remarkable seeds that are like buttons about half an inch in diameter. The wood is valuable, sold under the name of ebony in India.
The Pea family is among the largest flowering plant families with about 18,000 species in 630 genera worldwide. Caesalpina is the type genus for the Fabaceae subfamily Caesalpinioideae, following Cronquist (1981). This subfamily is intermediate in flower morphology between the other two higher-level classifications Mimosoideae and Faboideae (or Papilionoideae). The latter and largest group includes plants with papilionaceous, "butterfly-like", corollas (with standard, wings, and keel)—as the common garden pea.
All subfamilies are well represented on campus for closer study. Caesalpinioideae and Mimosoideae include mainly tropical trees with pinnately or bipinnately compound, alternate leaves. Mimosoideae flowers are regular (radially symmetrical), the corolla with equal petals often fused into a tube. Campus representatives include Acacia, Albizia, and Gymnocladus. Caesalpinioideae flowers are usually more or less zygomorphic (divisible into equal halves in one plane only). As with Caesalpina spp., the petals are distinct, the uppermost often smaller than the laterals. Other campus members of the subfamily include Bauhinia, Cassia, Cercis, Gleditsia, and Parkinsonia. It would be instructive to work out the higher classification of the many other campus peas (genera listed in the family index) from field observation throughout the year.
— further reading: Wendy Zomlefer, Guide to Flowering Plant Families, Univ. of North Carolina Press, 1994.
Name derivation, genus | species after Johann and Caspar Bauhin, Swiss botanists | variegated (the flowers)