Fig. 5.3-7. Transverse section through leaf of water lily. The large, branched red structure that extends from the upper to the lower epidermis is an astrosclereid. The defining characters are that it has a lignified secondary wall (indicated by the red stain) and that it is branched. An unusual feature of astrosclereids in water lily is that they are so large – this is a single cell, big enough to span the entire width of the leaf as well as branch in various directions. It is so wide that parts of it do not fit into the section, and the microtome knife has cut away the back wall and the front wall of the top of the sclereid (the area where it appears white at the top). The white area in the center of the sclereid is where an arm that came up toward us was cut off by the microtome.