Ashingtonia Volume 1 number 5, March 1974
FRAILEA PHAEODISCA (Speg.) Speg.
by A. F. H. Buining
syn.: Echinocactus pygmaeus var. phaeodiscus Speg. in Cact. Plat. Tent.,498, 69.1905 Frailea phaeodisca (Speg.) Speg. in Notas.Cact.,1923,73, No.XI.
Frailea phaeodisca was described in 1905 by Spegazzini as a variety of the plant now known as Frailea pygmaea (Speg.) Br. & R. but in 1923 he classified it as a distinct species.
Castellanos in his Revision de las Cactaceas Argentinas, III, makes Frailea castanea Backeb. & Knuth and Frailea asterioides Werd. synonyms of Frailea phaeodisca. This must be wrong and it can only be supposed that Castellanos had never seen Frailea asterioides and knew it only from Werdermann's description.
I have had the opportunity to collect Frailea phaeodisca several times in the southern and south western parts of Brasil, Rio Grande do Sul, where it occurs on bare rocky places and also in wetter areas amongst mosses.
The little plant body is simple with a long tapering root system. Above ground it is 10-20mm high and up to 35mm in diameter. It has a very typical dark green to dark brown epidermis. It has 22-26 ribs composed of absolutely flat tubercles with the ribs separated only by a dark vertical line. The oval areoles are very typical with their violet-black felt cushions. The thin spines are straight and lie flat against the plant body and are pectinate to radiate in display. There are 10-14 radial spines, all white with thickened brownish black bases, and no centrals. The spines have fine hairs not shown by those of Frailea pygmaea. The yellow flower compared with the size of the plant body is quite large: 22 (-25)mm long and wide. The scales on the pericarp and receptacle bear brown bristles and greyish white hairs in their axils. The outer and inner perianth segments are yellow and spathulate. The whitish stigma lobes are exserted beyond the yellow anthers on the filaments. The almost globose fruit bears brown bristles and greyish white hairs. The seed is boat shaped, 2.5-3mm long and 1.5-2mm wide, with a dark brown shiny smooth testa and an oval basal hilum; the embryo is conical.