Placenta (pl. = placentae)
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Title
Placenta (pl. = placentae)
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Definition
The tissue within an ovary to which the ovules are attached or closely associated.
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Notes
Defining that part of the ovary can be interpreted differently. We define a placenta of as the tissue derived from a single carpel. Do not confuse this interpretation with the placental tissue derived from adjacent locules---this fusion of placental tissue we call a septal head unit. In both cases, the number of placentae in an ovary is the same as the number of locules. The placentae of neotropical Lecythidaceae provide characters for distinguishing genera, e.g., the placenta of speces of Gustavia is expanded and located at the apex of the locule, and the ovules are not pendulous. Those of Grias are also at the apex of the ovary but they are not expanded and the ovules are pendulous). Other clades of neotropical Lecythidaceae also have features that help delimit them but the features are not as clear cut as those of Gustavia and Grias.
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Related Terms
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