AntherThe part of a stamen that makes pollen. It sits on the filament.
FilamentThe stalk of a stamen. It carries the anther.
Pollen sacs (microsporangia)The four chambers where pollen forms. They lie in two pairs.
ConnectiveThe tissue that joins the two halves of the anther. It continues the filament.
Vascular bundleThe strand that carries water and food into the anther.
StomiumThe line where the anther splits open. Pollen leaves through the slit.
One pollen sac 7
TapetumThe innermost wall layer. It feeds the cells that become pollen.
Pollen mother cellsEach one divides into four young pollen cells.
EndotheciumThe wall layer with thickened bands. It helps the anther open.
EpidermisThe outer skin of the anther. It covers the other wall layers.
Middle layersThin wall layers that flatten and break down as the anther ripens.
TetradsA group of four young pollen cells from one mother cell.
Pollen grainsThe ripe grains, each grown from one cell of a tetrad.
How this list was compiled: Every name checked on 2026-10-03 and kept only where two of these use it. (1) J. M. Coulter and C. J. Chamberlain, Morphology of Angiosperms, 1903, chapters III and VI (public domain), https://archive.org/details/morphologyofangi00coulrich : figure 7 is a transverse section of an almost mature anther of Lilium philadelphicum, with the stomium and the endothecium (with its rib-like thickenings) very prominent and nearly all the walls separating the microsporangia broken down; in most cases the stamen produces four microsporangia; the vascular strand of the connective; within the epidermis the outermost parietal layer generally becomes the endothecium, whose cells develop thickening bands; between the outermost and innermost parietal layers there are usually one to three middle layers, whose cells gradually become flattened and disorganized; the innermost layer becomes part of the tapetum, a jacket of nourishing cells in contact with the sporogenous tissue; pollen mother-cells (microspore mother-cells) each form a tetrad of four microspores by two divisions; dehiscence by a longitudinal fissure, a definite stomium developing, as in Lilium, opening by the drying of the anther walls. (2) Wikipedia, Stamen, Microsporangium, Tapetum (botany), Dehiscence (botany), https://en.wikipedia.org/wiki/Stamen , https://en.wikipedia.org/wiki/Microsporangium , https://en.wikipedia.org/wiki/Tapetum_(botany) , https://en.wikipedia.org/wiki/Dehiscence_(botany) : a stamen has a stalk, the filament, with an anther; a typical anther contains four microsporangia, also called anther sacs or pollen sacs; the tissue between the lobes is the connective, the filament's extension, with conducting strands (a vascular bundle in the figure of the section); the wall layers from the outside are a single layer of epidermis, a single layer of endothecium with fibrous thickenings, one to three middle layers that generally disintegrate, and the tapetum, a nutritive layer; pollen mother cells undergo meiosis; the spores may stay together in a tetrad; each microspore becomes a pollen grain; the stomium is where the anther splits open (dehiscence), and the endothecium makes the tensions that split the anther as its cells lose water. (3) E. Strasburger, F. Noll, H. Schenck and A. F. W. Schimper, A Text-Book of Botany, second English edition, 1903 (public domain), https://archive.org/details/textbookofbotany00stra_1 : the stamens are divided into the filament and the anther; the anther as a rule consists of two thecae and the connective between them, and each theca contains two pollen-sacs; figure 359 is an almost ripe anther of a daylily cut across, with the groove in the connective and its vascular bundle, and part of a pollen-sac with the pollen mother cells, the tapetal layer, an intermediate layer that becomes compressed, a layer of eventually fibrous cells and the epidermis. Licence: own work
The drawing: Drawn for this site on 2026-10-03 from plain geometry; own work, nothing traced. Licence: own work
How it works
Lilium anthers labeled here are cut across, as a microscope slide shows them: four pollen sacs joined by a connective. The second drawing enlarges one young sac, from its wall layers in to the pollen mother cells.
Read the full guide
The cut face
A stamen is a filament that carries an anther. Cut across, the anther shows four pollen sacs, two on each side of the connective, with a vascular bundle in the middle. The stomium marks where each side later splits to shed pollen.
Inside one pollen sac
From the outside in, the wall is the epidermis, the endothecium with its thickened bands, one to three middle layers, and the tapetum, which feeds the cells inside. Each pollen mother cell divides twice, by meiosis, into a tetrad of four microspores. Each microspore becomes a pollen grain.
In a nearly ripe lily anther the wall between the two sacs of each side has broken down, so a slide may show two chambers.
The drawing shows every wall layer at once. In a real anther the middle layers and tapetum fade as the pollen ripens.
Questions and answers
How many pollen sacs does a lily anther have?
Four. They lie in two pairs, one pair on each side of the connective. Botany texts call them microsporangia.
What is the tapetum in an anther?
The innermost layer of the pollen sac wall. Its cells lie next to the pollen mother cells and nourish them and the young pollen.
What does the endothecium do?
It helps the anther open. Its cell walls carry thickened bands, and as the anther dries the layer pulls the wall apart along the stomium.
What is a tetrad in an anther?
A group of four young cells, the microspores, made when one pollen mother cell divides twice. Each of the four becomes a pollen grain.