There are no leaves. Sargasso Weed is a type of brown algae, which means that it does not form true leaves, stems, or roots. The leaf-like structures are called blades, and the stem-like structures are called stipes. Back in the dark ages, when I was a kid, these algae were considered to be plants because they had chlorophyll, but now they are in a separate kingdom, Chromalveolata.