Final answer:
Secondary growth in stems, increasing the plant's thickness, is typical in dicots and gymnosperms, not monocots or mosses.
Step-by-step explanation:
Secondary growth in stems, which refers to an increase in the thickness or girth of a plant, is typically seen in dicots and gymnosperms. Monocots usually do not exhibit secondary growth; instead, their primary growth may allow for some lignified tissues that provide a degree of strength and support, as seen in plants like bamboo and palm trees. When considering the evolutionary origins of secondary growth, it is evident that it has evolved multiple times across different plant lineages. However, in modern plants, the presence of secondary growth is prominently observed in eudicots and other gymnosperms such as conifers and cycads.
Gymnosperms are known for a wide variety of species, like conifers and cycads, which show secondary growth, while mosses, being non-vascular plants, do not exhibit secondary growth at all. Overall, the most significant occurrence of secondary growth can be found among dicots (or eudicots), which comprises two-thirds of all flowering plants.