Laticifers: an historical perspective

This review describes the development of the laticifer concept, with emphasis upon the nonarticulated type, from early observations of plant exudates and "juices" to the presentation of laticifers by Esau (1953). Classical writers and herbalists described practical applications of these substances. With the advent of the microscope early investigators believed that these substances occurred in structures present in most, if not all, plants and, wrongly, equated these structures to the circulatory system in animals. Introduction of the term, latex, into botany derived from its early use as a term for a blood component by physicians, and not for analogy to milk. However, the origin of the terms, laticifer and laticiferous, remains uncertain. Initial studies of laticifers were marked by the controversy of whether they represented intercellular spaces or elongated cells. Confirmation of their cellular character led to the designation of nonarticulated and articulated laticifers. Nonarticulated laticifers were shown to arise during early embryogeny in some plants. The ontogenetic origin of the articulated laticifer was unclear to early workers, but new laticifers were detected to be formed by cambium activity. Nonarticulated laticifers were described to develop by intrusive growth whereby tips of the cell penetrated between adjacent cells. The coenocytic condition of the nonarticulated laticifer resulted from nuclear divisions along the cell positioned in the growth region of the shoot and the subsequent distribution of the daughter nuclei along the length of the cell. /// Die vorliegende Übersicht beschreibt die Entwicklung des Milchröhrenkonzeptes, beginnend mit den frühen Beobachtungen an Pflanzenausscheidungen und "Pflanzensäften" bis hin zu ihrer Darstellung bei Esau (1953). Dabei stehen ungegliederte Milchröhren im Vordergrund. Die klassischen Schriftsteller sowie die Verfasser der Kräuterbücher haben die Nutzanwendungen dieser Stoffe geschildert. Mit der Erfindung des Mikroskops wurden frühe Forscher zu der Annahme verleitet, daß derartige Stoffe in Strukturen vorkämen, die den meisten, wenn nicht allen Pflanzen gemeinsam seien. Diese Strukturen wurden dann, fälschlicherweise, mit dem Kreislauf der Tiere homoligisiert. Die Einführung des Begriffs "Latex" in die botanische Terminologie beruht auf der frühen ärztlichen Verwendung dieses Begriffs für einen Blutbestandteil, und nicht auf einer Analogie zu Milch. Die genaue Herkunft der Bezeichnungen "Milchrö