The middle layers had a common histogenetic origin with the endothecium. It was detected by the microspore tetrad stage (Fig.
The walls of the endothecium thickened after the microspores formed (Fig.
However, the classic model of anther development involving three 'germ layers' that give rise to specific cell lineages (LI to epidermis, L2 to endothecium
, middle layers, outer tapetum and archesporial cells, and L3 to connective and inner tapetum) and the well accepted dual origin of tapetum in angiosperms, has been challenged.
The young anther wall in S.striata consists of four layers from outer to inner, an epidermis, endothecium, one middle layer and taptum (Fig.
During meiosis, the cells of endothecium layer are tangentially elongated and have spiral thickenings which are made of lignin.
Development of anther wall follows the dicotyledonous type, which is composed of an epidermal layer, an endothecium
layer, one middle layer and tapetum.
The species of Enkianthus differ from other Ericaceae in having anthers with fibrous endothecium, monadinous pollen without viscin threads, and seeds with vascular bundles in the raphe, but these features may represent symplesiomorphies, and as such they are not diagnostic of the genus.
The stamens are twice the number of the corolla-lobes and have anthers that are smooth to distinctly papillose, opening with longitudinal slits by means of a fibrous endothecium. The anthers have awned appendages, which gradually narrow from the thecae, and the filaments are variously papillose to hairy.
From the cross section we see that the anther wall consists of five layers from outer to inner: an epidermis, endothecium
, two rows of middle layer and a layer of tapetum (Fig.
THE LOCULE SURROUNDING EXTERNAL LAYERS: EPIDERMIS, ENDOTHECIUM
, AND MIDDLE LAYERS
On maturation of the anther, the sporangial wall consists of the epidermis and the endothecium
, whereas the middle layers and tapetum disintegrate.
He removed the pollen grains and pollenkitt from a dehisced anther and then detached the tapetal membranes on the inner tangential endothecium
wall together with the orbicules.