Final answer:
Robert Brown used the unique shapes and sizes of pollen grains to classify plants. Pollen develops in the anther and is important in palynology for interpreting past climates and tracking plant migration over time.
Step-by-step explanation:
In the early 19th century, Scottish botanist Robert Brown observed that pollen grains could be used to classify plants due to their unique shapes and sizes. Pollen grains develop in the anther of a flower, and this botanical feature has practical applications in fields such as agriculture, where plant breeders may transport seeds to different areas, and palynology, the study of pollen and spores. The morphology of pollen fossils is particularly useful for interpreting paleoclimate, as these durable structures are preserved in the sedimentary record and reflect the types of plants that were present in ancient times. Through palynology, the examination of fossil pollen from various plant species, such as those depicted in Figure 11.9, scientists gain insights into past climates and can even trace the migration of plant species in response to climate change. These applications underscore the significance of pollen not just in plant biology, but in ecological and environmental research as well.