Vietnam or Thailand ? Vote for the TOP Country of the Week !
Updated: May 17, 2025
Here we may assume that the old Draba verna has produced a host or a swarm of new types. Thence they must have spread over Europe, but whether in doing so they have remained constant, or whether some or many of them have repeatedly undergone specific mutations, is of course unknown.
Let us begin with the sharpness of the varietal characters. In this respect varieties differ most obviously from elementary species. These are distinguished from their nearest allies in almost all organs. There is no prominent distinctive feature between the single forms of Draba Verna, Helianthemum or of Taraxacum; all characters are almost equally concerned.
It demonstrates the existence of polymorphous genera, such as Draba and Viola and hundreds of others. They clearly indicate a previous state of mutability. Their systematic relation is exactly what would be expected, if they were the result of such a period. Perhaps mutability has not wholly ceased in them, but, might be found to survive in some of their members.
There is no danger that lamarckiana might die out from the act of mutating, nor that the mutating strain itself would be exposed to ultimate destruction from this cause. In older swarms, such as Draba or Helianthemum, no such center, around which the various forms are grouped, is known. Are we to conclude therefore that the main strain has died out?
In my opinion we have the right to assume that if Draba and violets and others have formerly mutated in this way, other species must at present be in the same changeable condition.
The main fact is, that such a small species as Draba verna is not at all a uniform type, but comprises over two hundred well distinguished and constant forms. It is readily granted that violets and whitlowgrasses are extreme instances of systematic variability. Such great numbers of elementary species are not often included in single species of the system.
It must be borne in mind that an ordinary systematic species may include many dozens of elementary forms, each of which remains constant and unchanged in successive generations, even if cultivated in the same garden and under similar external conditions. Leaving the violets, we may take the vernal whitlow-grass or Draba verna for a second illustration.
Of these only the two former were seen in the spring, and by far the greater number killed were of the first-mentioned species. They usually had in their maws the leaves of the Dryas Integrifolia, buds of the Saxifraga Oppositifolia, Salix Arctica, and Draba Alpina, the quantities being according to the order in which the plants have here been named.
But why this should affect the foliage in one manner, the flowers in another and the fruits in a third direction, remains obscure. To gain ever so little an insight into the nature of these changes, we may best compare the differences of our evening-primroses with those between the two hundred elementary species of Draba and other similar instances.
But obviously this is only of secondary importance, and has no influence on the fact that a number of new types, analogous to the older swarms of Draba, Viola and of many other polymorphous species, have been seen to arise directly in the wild state.
Word Of The Day
Others Looking