sticking with the euphorbs
and christmas themed plants…
Did you know that the red “flowers”of the poinsetta plant are not flowers but modified leaf bracts? Poinsettias are in the Euphorbiaceae, or Spurge family, a group that is characterized by the oft present bracts and a milky, often toxic, latex sap. the plants also are unisexual! with the female (pistillate) and male (staminate) flowers occuring on the same plant. the ovary is always positioned superior, and it consist of 3 (or 4 or 5) united carpels with partition walls.
This native-to-Mexico spurge, Euphorbia pulcherrima is also a “long-night” plant, meaning that it forms flowers and its bracts change color as the day light hours lessen (read: it needs the long, dark hours of fall and late summer to produce its awesome red bracts and make cycathium). this response is called light/darkness is called photoperiodism. if you were to pulse an artificial light on the plants in the dead of the night the plant would not produce flowers. however, as much of the darkness that this plant needs, it also requires bright sunlight to have the brightest red colouring.
the poinsettias are in the tribe Euphorbieae and the subtribe Euphorbiinae (genera Euphorbia, hence Euphorbia pulcherrima) which are characterized by a non-flower infloresence called a cyathium. great pics of this modified “non-flower” are here: http://waynesword.palomar.edu/terminf2.htm