The depicted example from the botanical garden Todaifuzoku-Tokyo is of historical interest:

"The spermatozoid of Ginkgo biloba was first discovered in seeds of this female tree by Sakugaro HIRASE, who was a teaching assistent in the Botanical Institute, Imperial University, and was studying the fertilization and embryo development in Ginkgo. This finding is believed one of the most important contributions from the early days of Japanese botany"

(plaque at the bottom of the tree).
S. HIRASE discovered the spermatozoids on the 9^th of September 1896. He reported his findings on the 26^th of September of the same year in the Tokyo Botanical Society. (literature about this: Y. OGURA: Phytomorphology 17, 109 - 114 (1967)).