实际上上述说法并不确切.按wiki:

In 1827, while examining pollen grains and the spores of mosses and Equisetum suspended in water under a microscope, Brown observed minute particles within vacuoles in the pollen grains executing a continuous jittery motion.

布朗发的原始文章的题目也是:

"A Brief Account of Microscopical Observations
Made in the Months of June, July, and August, 1827, on the Particles Contained in
the Pollen of Plants; and on the General Existence of Active Molecules in Organic
and Inorganic Bodies"

请注意实际是花粉颗粒的里面的微粒的无规运动,这个东西应该比花粉小的多,这样布朗运动才会比较明显.