regmacarp

The fruit of the common milkweed (Asclepias syriaca) is a regmacarp; when mature, it dehisces or splits open to release its seeds.

From Ancient Greek ῥῆγμα (rhêgma, “something broken or rent asunder; a breach, cleft, fracture”) (possibly ultimately from Proto-Indo-European *bʰreg- (“to break”)) + English -carp (suffix meaning ‘part of a fruit or fruiting body’) (ultimately from Proto-Indo-European *kerp- (“to harvest; to pluck”)), modelled after schizocarp. The word was probably coined by the Scottish physician and botanist William Ramsay McNab (1844–1889): see the 1871 article from the journal Nature quoted below.

• (Received Pronunciation) IPA^(key): /ˈɹɛɡməkɑːp/

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• (General American) IPA^(key): /ˈɹɛɡməkɑɹp/
• Hyphenation: reg‧ma‧carp

regmacarp (plural regmacarps)

1. (botany, obsolete, rare) A fruit which, when mature, splits open to release its seeds; a dehiscent fruit. [from 1871]
   • 1871 October 12, W[illiam] R[amsay] McNab, “Remarks on the Classification of Fruits”, in Nature: A Weekly Illustrated Journal of Science, volume IV, London, New York, N.Y.: Macmillan and Co., →OCLC, page 475, column 2:

     Taking the word Schizocarp as a type, I venture to suggest the term Achænocarp for the group of Achænes as used by Dr. [Alexander] Dickson, thus avoiding all confusion, and allowing the term Achæne to remain in its restricted sense. Regmacarp I would apply to the group of capsules, using the term capsule for one division of the group. […] The derivation of these terms at once explains their application. […] Regmacarp from regma, a rupture, in allusion to the dehiscence. […] In using these terms I would employ them in the following manner:— […] II. Dry Dehiscent Fruits. 3. Regmacarps. A. Follicle. Simple, dehisces by one suture. […]

   • 1874, Robert Brown, “The Fruit”, in A Manual of Botany: Anatomical and Physiological: For the Use of Students, Edinburgh, London: William Blackwood and Sons, →OCLC, pages 482–483:

     The truth is, that it is impossible to find a classification of fruits which is founded on strictly scientific principles—the forms merging into each other; […] Accordingly, in the following classification, in which we have mainly followed Dr [Maxwell Tylden] Masters, all the less easily defined forms are omitted, and the list reduced as much as possible, without at all destroying its usefulness. […] monothalmic fruits. A. Ripe pericarp uniform. […] Fruits dehiscent.—II. Pods, or Regmacarps—viz., Follicle, Legume, Siliqua, Capsule, Pyxis.

   • 1879, Asa Gray, “The Fruit”, in The Botanical Text-book. Part I. Structural Botany or Organography on the Basis of Morphology. […], 6th edition, London: Macmillan and Company, →OCLC, section II (The Kinds of Fruit), paragraph 555, footnote 1, page 292:

     Dr. Master's [i.e., Maxwell T. Masters'] modification of [Alexander] Dickson's and [William Ramsay] McNab's classification of simple fruits, as to primary kinds, is into 1. Nuts, or Achænocarps, dry and indehiscent; 2. Pods, or Regmacarps, dry, dehiscent; 3. Stone-fruits, or Pyrenocarps, fleshy without, indurated within, indehiscent; 4. Berries, or Sarcocarps, fleshy throughout, indehiscent.

• regma
• regmaglypt
• regmaglyptic

• dehiscence (botany) on Wikipedia.Wikipedia