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Both are true elementary species, differentiated from lamarckiana in nearly all their organs and qualities, but not showing any preponderating character of a retrograde nature. Their differences may be compared with those of the elementary species of other genera, as for instance, of Draba, or of violets, as will be seen by their description.
Farther away from this center they are more widely dispersed, each holding its own in its habitat. In all, Jordan has distinguished about two hundred species of Draba verna from Europe and western Asia. Subsequent authors have added new types to the already existing number from time to time.
Violets and Draba verna, dandelions and helianthemums and many other instances were dealt with in previous lectures. Even wheat and barley and corn afford instances of large groups of elementary species. Formerly mixed in the fields, they became separated during the last century, and now constitute constant races, which, for brevity's sake, are dealt with under the name of varieties.
The observation of the production of mutants in the field at Hilversum, and the subsequent cultivation of the new types in the garden at Amsterdam, gives ample proof of the mutability of plants. Furthermore it furnishes an analogy with the hypothetical origin of the swarms of species of Draba and Viola.
The pebbly fragments of the entire slope, which during spring-time were sparingly covered with dwarfish herbs, such as the Androsace occidentalis, Draba Caroliniana, Plantago Virginica, Scutellaria parvula, are now crowded with plants of taller growth and variegated blossoms.
Starting from this conception the pedigree of our mutations must be considered as only one small group. Instead of figuring a fan of mutants for each year, we must condense all the succeeding swarms into one single fan, as might be done also for Draba verna and other polymorphous species.
On the contrary we find elementary species in different genera based on the greatest possible diversity of features. The forms of Taraxacum or Helianthemum do not repeat those of Draba or Viola. In roses and brambles the distinguishing features are characteristic of the type, as they are evidently derived from it and limited to it.
The rest of the vegetation consisted of a Sedum, Nardostachys Jatamansi, Meconopsis horridula, a slender Androsace, Gnaphalium, Stipa, Salvia, Draba, Pedicularis, Potentilla or Sibbaldia, Gentiana and Erigeron alpinus of Scotland. The broad top of the hill was also of quartz, but covered with angular pebbles of the rocks transported from Kinchinjhow.
Sagina apetala and patula, Spergula media and salina and many other pairs of allied species have differentiating characters of the same value as those of the elementary species of Draba verna. Filago, Plantago, Carex, Ficaria and a long series of other genera afford proofs of the same close relation between smaller and larger groups of species.
The elementary species of Draba are characterized, as we have seen, by the forms and the hairiness of the leaves, the number and height of the flower-stalks, the breadth and incision of the petals, the forms of the fruits, and so on. Every one of the two hundred forms included in this collective species has its own type, which it is impossible to express by a single term.
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