Plants with hysteranthous leaves, clump forming, inflorescence up to 115 mm high. Tuber pyriform, horizontal, solitary or more frequently forming multiple tubers by growing rhizomes. Tubers about 18 mm long and 10 mm wide. The rhizomes develop growing points and then more rhizomes thus forming chains about 100 mm long and up to 10 mm wide. Skin light chestnut brown, leathery, tuber interior white; growing point apical or lateral. Old leaf sheaths up to 35 mm long, 3 mm wide, chestnut brown, membranous. Leaf one per growing point, erect; contemporary leaf sheath exserted up to 25 mm, nearly 1 mm wide at the base becoming broader and grooved near the lamina, glabrous; lamina broadly or narrowly elliptic, sometimes cordate, up to 30 mm long and 17 mm wide or 60 mm long and 12 mm wide, apiculate, adaxial surface bright green, abaxially lighter green; margin slightly crisped. Peduncular bract sheathing part exserted about 20 mm, dark red, non-sheathing part spreading, ovate with a recurved apex, 8 mm long, 5 mm wide, green. Peduncle up to 85 mm long, green, glabrous. Raceme subcorymbose, up to 40 mm long and 40 mm wide, with 4-15 flowers. Bracts triangular, closely adpressed to the pedicels, 0.5 mm long, white, membranous. Pedicels up to 18 mm long, arcuate. Flowers spreading to recurved when fully open in late afternoon, 12 mm diameter. Tepals sub-equal, connate for the first 1 mm, bright yellow with a green midnerve on the outside, sometimes covered with red streaking; outer linear, 8 mm long, 1.5-1.8 mm wide; inner narrowly spathulate, 7 mm long and up to 2 mm wide. Filaments erect, equal, filiform, 6 mm long, 0.5 mm wide at the base and tapering very gradually, yellow; anthers small, yellow. Ovary ovoid 2.5 mm long, 1.5 mm wide, pale green. Style cylindrical, 3.5 mm long, yellow.
E. macgregoriorum is closely related to E. corymbosum but is separated from that species by its considerably smaller peduncular bract and longer peduncle. The characteristic chains of rhizomes have not been observed in other species.
This species is so far known only from the Nieuwoudtville to Calvinia area, where it may be fairly common.
It is found on flats of heavy soils especially on the red, dolerite-derived soils. In mid-winter and spring leaves may be difficult to spot amidst the prolific annual growth of surrounding plants.
Flowering time: February to March.
Leafing period: April to October.
This species is named in honour of the MacGregor family, on whose farm the type specimen was collected by Mark MacGregor. Neil Macgregor sets an example among farmers for guardianship of the native flora and promotes farming practices to preserve and encourage the flowering of rare geophytes.