La formation d' « embryons végétatifs » chezDaucus carotaL.

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Abstract
Summary—Vegetative embryoids have been obtained from the wild carrot and several cultivated varieties. In accord with the results of HALPERIN and WETHERELL (1965), the NH4 + ion greatly enhances embryogenesis, in contrast to the NO3—ion. Numerous embryoids have been obtained on primary explants without any transfer to a medium with a lower auxin level. Amongst the 8 auxins tested, 2-naphthoxyacetic acid at 10−5M was the most effective one in stimulating embryo formation. Abscisic acid did not block embryogenesis, but. slowed down development and prevented chlorophyll formation in the cotyledons. The morphological entities produced are bipolar axes with an apical bud and a root; they produce typical cotyledons; at least some of them presumably arise from single cells; they undergo the morphogenetical stages which are characteristic of zygotic embryos. For all these reasons, they should be called « embryos », as are the adventive embryos of Citrus.