Coryphantha durangensis

Structure and identification

The monograph describes ovoid or columnar stems with a densely woolly apex and basal offsets. Flat, rhomboid tubercles overlap like roof tiles. Lateral spines are thin. Upper ones may be much longer than lower ones. In the nominate group, a single dark central spine points upwards or is absent. Pale yellow flowers have a reddish stripe on the outer tepals. [Dicht and Lüthy 2005, p. 148–149]

Habitat and variation

The monograph associates the nominate group with rocky slopes of volcanic hills in eastern Durango and neighbouring Coahuila. Material described as subsp. cuencamensis differs in having more tubercles and stronger armature, and its sites lie on limestone gravel beneath shrubs. Information about these groups retains the distinction made in the source. [Dicht and Lüthy 2005, p. 148–149]

Seed position and germination

Seeds collected in April 2009 from at least ten plants in Cañón de Fernández, Durango, were sown on the surface or buried 0.5 cm deep. Soils from beneath mesquite and from an open area were compared. Each of the four treatments included five replicates of 20 seeds, or 100 seeds each. Within a month, 96% of surface seeds germinated in soil from beneath mesquite and 56% in soil from the open area. After burial, the figures were 2% and 0%, respectively. [Muro-Pérez et al. 2014, p. 345–347, ryc. 1B]

Seed position was strongly associated with the result, and soil type also differentiated surface germination. The authors linked the burial effect partly to reduced light. Light, soil properties and the covering itself were not separated into independent factors, so this experiment primarily shows the advantage of surface seed placement in the arrangement used. The subsequent fate of non-germinating seeds was not assessed. [Muro-Pérez et al. 2014, p. 346–348, dyskusja]

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