| Popis: |
The cortical-bundle system of the composite genus Adenocaulon has been studied from material of A. lyratum, A. bicolor, A. chilense, A. himalaicum, and A. adhaerescens. In A. lyratum, A. bicolor, and A. himalaicum three cortical bundles or groups of cortical bundles extend longitudinally through the stem. In A. adhaerescens, there are a large number of cortical bundles not organized into groups; a cortical-bundle system is absent in A. chilense. In the species with distinct cortical-bundle groups, at each node, two of the bundles or groups of bundles give rise to six leaf traces, while the stele contributes three. The cortical bundles are believed to be morphologically equivalent to the veins of portions of stipules that have become adnate to the stem. Evidence for the stipular origin of the cortical bundles is most obvious in A. lyratum; the condition present in the other species suggests reduction. The term "accessory cortex" is proposed for the cortex of Adenocaulon, where the apparent cortex of the st... |
