Sapium haematospermum Müll.Arg. presents two different laticifer systems, distinguishable on the basis of their structure and ontogeny. Although they are both articulated anastomosing laticifers, produced from procambium and (or) ground meristem, they vary in diameter and in the presence or absence of starch. One of them, originating near the promeristem and leaf primordia, is composed of straight, wide laticifers with rod-shaped starch grains, whereas the other one is made up of narrow and sinuous laticifers that arise in expanding organs. The two systems are observed in almost all tissues of the leaf and in the cortical parenchyma and vascular tissue of the stem. Our results show the presence of two different laticifer systems for the first time in Sapium and contradict former reports that described nonarticulated laticifers in this genus. The occurrence of two different laticifer types in the same genus, and indeed the same plant, is extremely rare. The milky latex of the two laticifer systems of S. haematospermum, which consists of terpenoids, fatty acids, phenolic compounds, proteins, and polysaccharides (including mucilage), plays an efficient role in sealing wounds, blocking microorganisms, and avoiding herbivory.

The histochemical characterization of the oleoresin produced by secretory ducts of Artemkiu campestris ssp. maritima revealed the presence of terpenoids (essential oils, resiniferous acids and probably steroids), alkaloids and fatty acids, eventually polyacetylenes. The ultrastructural study of A. campestris ducts enabled us to consider that the secretory activity begins very early during the duct development. The oleoresin deposited in the duct cavity is produced by epithelial and sub‐epithelial cells that contain, at the secretory phase, a great amount of smooth endoplasmic reticulum (SER) surrounding plastids with few thylakoids. These organelles may play an important role in the oleoresin production, the SER probably being responsible for some steps in the biosynthesis of oleoresin components and for the transport of the secreted material towards the plasmalemma. Endoplasmic reticulum and mitochondria probably have a role in the synthesis of steroids. After secretion, the duct glandular cells degenerate progressively. The extrusion process of secretion may be considered mero‐holocrine.

.Summary.-The secretory trichomes from Artcmi.fia crithmifolia present a I.Jiscriate multicellular structure. They originale from a single epidrrmal cell, belonging to the leaf orto the ~tem primordia. Histochcmical tests reveal the lipophilic character of the secreted matcrial corresponding probably to terpenoids.Young trichome cells possess the normal features of a secretory cel!, namely a dense cylo· plasm conlaining numerous mitochondria and plastids and few vacuoles. A large nucleus with one or more prominenl nucleoli is also present.Modifications of plastids morphology and increase of ER profiles must be rclated to sccre· tion. Osmiophilic droplets are seen in close relation with plastids and ER. Electron dense matcrial has also been observed in small vacuoles, corresponding presumably to the storage of secretion.Secretory products are extruded and temporarily accumulatcd in the subcuticular space. Older trichomes undergo a lytic process followed by trichomes death.Résumé.-Les trichomes sécréteurs d'Artemisin crithmifolia sont formés par plmieurs cd· Iules à disposition bisériée. Ils proviennent d'une cellule épidermique appartenant soit à la feuille soit à la tige. Des tests histochimiques révèlent la nature lipophilique de la sécrétion. Il s'agit proba· blement de terpènes.Les cellules des jeunes trichomes présentent l'aspect caractéristique des cellules sécrétrice:.:, notamment un noyau très volumineux à un ou plusieurs nucléoles et un cytoplasme riche en ribo·

Micromorphology, histochemical and confocal analyses of the trichomes of Satureja subspicata (Bartl. ex Vis.) were carried out using light microscopy, confocal laser scanning electron microscopy (CLSM), and scanning electron microscopy. Non-glandular unbranched and two types of glandular trichomes - peltate and capitate - are described. The results of histochemical tests showed a positive reaction to phenolics, tannins, lipids, acid lipids, pectins and polysaccharides in both types of glandular trichomes. A strong red autofluorescence of the lipophilic and hydrophilic secreted material in glandular trichomes was observed with CLSM.

Colleters are secretory structures widely distributed in eudicots and with taxonomic value in many families. Although glandular trichomes have been described in some Anacardiaceae species, the chemical characterization of their secretions is scarce and to date there are no reports on colleters. Light microscopy and scanning electron microscopy were used to study the distribution and structure of colleters on the vegetative buds of Anacardium humile A.St.-Hil., Lithraea molleoides (Vell.) Engl., Spondias dulcis Parkinson, and Tapirira guianensis Aubl., and to characterize their secretory products histochemically. In all of these Anacardiaceae species, colleters are multicellular and multiseriate ovoid or club-shaped glandular trichomes of protodermic origin, present on both surfaces of leaf primordia. They reach the secretory phase at early stages of leaf development, after which they gradually degenerate, become brown, and fall off. Histochemical tests indicate that the secretion within the glandular cells and outside the trichomes is a complex mixture containing mucilage, fatty acids, and phenolic compounds, which are secretory products that can play an important role in the protection of meristems against desiccation and attack by pathogens. Therefore, the distribution of these glandular trichomes, their short-life, the chemical nature of their secretions and their presumed functions support their being classified as colleters.