Equisetum is a “living fossil”, the only living genus of the entire class Equisetopsida, which for over 100 million years was much more diverse and dominated the understory of late Paleozoic forests. some Equisetopsida were large trees reaching to 30 meters tall. It’s said that the horsetail plant inspired Scottish mathematician John Napier (1550-1617) in his development of logarithms. Sections of the horsetail stem shorten in a logarithmic or ‘telescopic’ fashion as they near the top. Logarithmic mathematics is also found embedded in the structure of seashells, pinecones, and elsewhere. i don’t know what mathematical formula dictated the beehive structure of the tops of these horsetails, but whoever invented it has my sincere thanks and admiration.
rough horsetail (Equisetum)