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Updated: May 16, 2025
The purple thorn-apple, which is considered by some writers as a variety of the white-flowered species or Datura Stramonium, and by others as a separate species, D. Tatula, will serve as an illustration.
Of the thorn-apples both species, the whiteflowered Datura Stramonium and the purple D. Tatula have such varieties. Spinach has a variety called the "Dutch," which lacks the prickles of the fruit; it is a very old form and absolutely constant, as are also the thornless thorn-apples. Last year a very curious instance of a partial loss of prickles was discovered by Mr.
It has also been contended that there is something to be said in favour of sudden, as opposed to exceedingly minute and gradual, modifications, even if the latter are not fortuitous. Besides these, the case of the Normandy pigs, of Datura tatula, and also of the black-shouldered peacock, have been spoken of.
More remarkable still, when crossed with the normal Datura tatula, hybrids were produced, which, in the second generation, reverted to the original types, as true hybrids do." There are, then, abundant instances to prove that considerable modifications may suddenly develop themselves, either due to external conditions or to obscure internal causes in the organisms which exhibit them.
Roxburgh if any particular kind was used in preference, and he said not; that both the above sorts were used; and, in fact, not only these, but the Datura Tatula, another species which grows wild there, and is cultivated in our stoves for the sake of its beautiful flowers, is also used for the same purposes.
But here we will limit ourselves to normal cases. The first example to be considered is obviously the assumption that the parents of a cross differ from each other in respect to two characters. A good illustrative example is afforded by the thorn-apple. I have crossed the blue flowered thorny form, usually known as Datura Tatula, with the white thornless type, designated as D. Stramonium inermis.
In 1861 that botanist observed, amongst a sowing of Datura tatula, the fruits of which are very spinous, a single individual of which the capsule was perfectly smooth. The seeds taken from this plant all furnished plants having the character of this individual. The fifth and sixth generations are now growing without exhibiting the least tendency to revert to the spinous form.
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