Sirocladium was described by Randhawa (type species S. kumaoense) on the basis of algal samples from damp soil at the margins of a waterfall in India. The genus is considered to be terrestrial and it is characterized by the presence only of two plate-like chloroplasts as well as by the occurrence of conjugation without tube formation. Currently, Sirocladium includes three additional species. S. maharashtrense Randhawa and S. vandalurense Randhawa are found on damp soils of India and S. cubense Rieth is known from humid soils of Cuba. The present study describes S. robustum, a new species of this poorly known genus of Zygnemataceae, whose specimens were collected growing on humid soil of a permanent puddle in the northwest region of the State of São Paulo, in Brazil. The higher dimensions of cells length and diameter, the zygospores dimensions and shape are the most distinctive characteristics of S. robustum from the other four species of the genus.
Brazil; Sirocladium robustum; soil; Zygnemataceae
