21. These fungal hyphae are usually what attach the thallus firmly to the substrate. 22. Apothecia have usually black concave discs, with exciple margins of thallus tissue. 23. A kelp, for example, may have its thallus divided into three regions. 24. Oakmoss thallus is flat and strap-like. 25. The grouping of the spores found in the thallus favors interpretation as a plant. 26. It forms calcium carbonate deposits within its cells which serve to strengthen the thallus . 27. The thallus attaches to a surface by means of small root-like rhizines. 28. This too can reproduce via monospores, which are produced inside the thallus itself. 29. The thallus of a crustose lichen has a patchwork or crazy-paving appearance. 30. They occasionally divide into equal secondary branches, usually well above the thallus base.
