cussed in this paper, present a problem of this kind. Mentzelia tindleyi and M. crocea are spring flowering annuals with rounded, papillose seeds and linear filaments. These characters place them in Sectioll Trachyphytwm, whereas their large, mucronate petals with some orange pigment at the base distinguish them from other members of this section. The only Mentzelias likely to be confused with M. lindleyi and M. crocea are M. gracilenta T. & G. and M. nitens Greene. Mentzelia gracilenta grows in the inner Coast Ranges generally south of M. lindleyi, and can be distinguished from M. lindleyi and M. crocea by its smaller, blunt or retuse petals. Mentzelia nitens occurs on the Mojave Desert and is most readily distinguished from M. tindleyi and M. crocea by the lack of orange pigment in its petals. The relationship of M. lindleyi and M. crocea to other members of Section Trachyphytum has been briefly discussed in a previous paper (Thompson and Lewis, 1955). Meentzelia ltindleyi is characterized by broad yellow-orange petals with a prominent orange spot at the base and by its habit, many individuals branching at or just above the ground level. Plants of this sort occur in the inner Coast Ranges of Central California. Mentzelia croc,ea differs in having narrower, yellow petals with a faint orange spot at the base and by branching well above