The seeds of Coryphantha spp. are generally reniform (only exception: C. gracilis with globular hat-like seeds). Sometimes they are somewhat longer or rounder and vary in size.
The measurements given are maximum length and width.
In a rounded impression on the flat side of the seed, there is the hilum and behind, slightly distant, the micropyle. The hilum is narrow and long to oval-shaped. It is slightly depressed and may be surrounded by a bulging prominence, which also includes the micropyle. The region of hilum and micro-pyle measures about one quarter to one half the length of the seed at the maximum. Characteristics of the seeds are illustrated in
The seeds of C. gracilis are very different. They are roundish with a very prominent roll around hilum and micropyle, which gives the impression of a hat or helmet. The hilum is also rounder than in other Coryphantha spp. (see Fig. 25).
The colour of the seeds is brown and varies from light to dark, sometimes also reddish. However, the colour of the seeds also depends on their stage of maturity. The surface of the seeds is shiny and smooth.
The borders of the outer testa cells are thick and bulging, which leads to a net-like structure. This form is called reticulate testa, which is obligatory for all Coryphantha species. The extent of these net lines varies from very fine (C. pseudoechinus) to quite large and prominent as in C. recurvata. Moreover, the form of the testa cells varies from nearly regularly hexagonal (C. pseudo-echinus) to very long as in C. tripugionacan-tha. However, the form of the testa cells and the formation of net lines are not identical on the whole surface of the seeds. Near the hilum they are much smaller and more densely set than on the rest of the surface.
The surface of the testa cells is granularly faceted in some species, but without any granular cuticular structures in others, which means completely smooth (see Figs. 26-29).
Fig. 24. Typical seed shapes. Left round, C. longicornis, middle reniform, C. octacantha, right longish, C. retusa
Fig. 26. Structure of testacells. Left C. pseudoechinus ssp.pseudoechinus, middle C. recurvata ssp. recurvata, right C. tripugionacantha
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