Lithops - Au Cactus Francophone

fig. 10 . lithops pseudotruncatella (bgr.) n.e. br.
PROBLEM OF DETERMINING SPECIES
OF THE GENUS
The delimitation of species in this genus is complicated by the fact
that the flowers of the various species show such little variation that they
cannot he used to any extent for purposes of classification. It is true that the
colour of the flower might be used, but whether this is a sufficient or safe
character to go by I am not prepared to say. It is well known that flower
colour frequently, depends on the kind of soil in which the plant grows. L.
Helmuti is a very distinct species. As has already been stated it has a yellow
flower and yet a white flowered form has been recorded. Is one justified in
creating a new species on this evidence alone? Another objection to the use
of flower colour in the delimitation of species is that these plants are usu
ally found in the vegetative condition and it sometimes takes years before
they flower. I have therefore discarded the flower as a systematic character
and have preferred to use the upper surface of the leaf for purposes of classi
fication. I do not want for a moment to say that the character chosen is
absolutely satisfactory, but what character is ? After all, our whole conception
of species is a subjective one. Some have a narrow idea of species and oth
ers prefer to draw a wider ring to include many different plants in a single
species. It sill be noticed that I have not mentioned—or at least only casu
ally—the size of the plants. So far as I can judge there is only one species, L.
Nelii which is characterised by its small size. The size of a succulent depends
to a great extent on the amount of water available. If the water supply is low
the plants are shrivelled and small, whereas after a rain these same plants are
larger, and one would hardly believe them to be the same wilted plants seen
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