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Abstract: In this paper the authors investigate the structure of the aerial vegetative organs of 2 species and 7 varieties of Rhododendron. The anatomical features of the analyzed taxons which could be useful in determination of the unflowered plants are underlined. The histo-anatomical featured with taxonomical value are: the shape, dimension and frequency of the hairs (tector and secretor), the presence or the absence of the crystalliferous cells, the thickness of the palisade parenchyma. Between the histoanatomical features with ecological signification - the xylem vessels diameter, the vesicular cells from leaf epidermis and thick cuticle, covered by wax - could be mentioned.
Key words: histology, species, varieties, Rhododendron
Introduction
The range of decorative plants specific to winter-spring season is further supplemented with a number of azalea species which have started to be largely grown since 1843 soon after Lielig's creation of "Aurora" species. Among the greatest azalea cultivating countries in the world we can mention: Belgium, Germany, France, Holland and Denmark (Kozel et al.,, 1971).
Plants of Asian origin, azalea is now wide-spread mainly in high mountain areas with high humidity, low temperatures, acid soils and intensely bright light. Today, Azalea species have invaded the European continent and can often be seen in greenhouses and botanical gardens.
According to Linné, the Ericaceae range consists of two species: the Rhododendron and the Azalea species. In most botanical treaties, the latter has been mixed with the Rhododendron (in R. group indicum), consisting of about 1000 species (trees or bushes displaying coriaceous leaves both permanent and deciduous) growing in Northern warm and temperate regions.
Using Brown's description (cf. Krusmann, 1962), the Rhododendron family consist in plants presenting scaly leaves - the lepidotes (species grouped into 19 classes) and scaless leaves - elepidotes (species grouped into 19 classes, e.g. Azalea which Rhodedendron is part of).
Rhododendron simsii Planch (sin. Azalea indica Ait., Rhododendron indicum Hemsl.), Azalea series, Obtusum sub-category, consists of trees no more than 3 meters tall, with thick hairy twigs that usually bloom during the winter-spring season. The species originate in the Eastern part of China and the Formosa Island.
There are two types of azalea: the Indian and the Japanese one. The former has large permanent flowers, about 2-6 within the inflorescence. This type...