Taxonomia e anatomia de Galinsoga ciliata (Rafin.) Blake

Resumo

This work deals with taxonomic and anatomical features of the species Galinsoga ciliata (Rafin, ) Blake, a plant ofthe Compositae family.

In addition to its systematic position, common names, description, geographic distribuition, flowering, reproduction, uses and some other observations are presented.

Anatomical studies were made on cross and longitudinal sections of leaves, stems, and roots.

The upper epidermis of the leaf has larger cells, with ticker cuticles, and less stomates than the lower one.

The stem was sectioned at different positions, in all the four internodes which usually comprise, plant, and a comparison of the tissues has being made. The epidermis has at first heterogeneous cells, becoming lately more homogeneous. Stomates and hairs decrease in number from the apex toward the basis. This cortex is made of parenchyma and collenchyma tissues, the latter being predominant in the younger internodes, but in the basal internodes it remains restricted to a single layer. The endodermis stands out in the second internode from the apex for is great amount of starch grains and absence of intercellular spaces.

The stele begins with a parenchymatous pericycle, which from the third internode down becomes sclerenchymatous. The phloem appears well differentiated in the last basal internodes.

The procambium, not very distinct at first, becomes a well differentiated cambium fromthe third internode. The xylem has primary structure in the two younger internodes, and secondary structure in the older ones.

The vascular strands are 12 in number all the way down through the stem. The pith almost does not change, and comprises most of the stem volume.

The root is made of the following tissues: epidermis, parenchymatous cortex, pericycle, phloem, xylem and parenchymatous pith. The pith, which at first comprises the bulk of the root, becomes relatively smaller and cross-shapéd (tetrarch) near the basis, in con- trast to the stem, which is dodecharch.