Fig.2. Stolons and stolonal mat of established colonies. (A) Section of a new stolon from a portion of a colony growing on a slide. The stolon is a tubular structure composed of an outer layer of ectoderm (Ec) surrounding an inner layer of endoderm (En) that lines the gastrovascular tube (GvT). The crystals (arrows) are confined to the endoderm and are intracellular rather than free in the gastrovascular tube. The dashed box encloses two crystals that are out of the plane of focus. Scale bar, 20µm. (B) New stolons growing from a portion of a colony recently transplanted to a microscope slide. New stolonal tubes (S) are separated by a layer consisting only of ectoderm (Ec). The crystals (arrows) are located within the endodermal cells that form the walls of the tube; the ectodermal cells that separate the tubes are devoid of crystals. The lower part of the section shows a crystalline mat (CM) below the living stolons, just out to the plane of focus. Scale bar, 200µm. (C,D) Comparison of the same section of the stolonal mat, grown on a coverglass and viewed from the underside by (C) brightfield and (D) polarized light microscopy. What appear to be dead, hardened stolon tubes (arrows) in C run throughout the stolonal mat. The dead tubes are refractile when observed by polarized light (arrows in D correspond to arrows in C). Scale bar, 200µm.
