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Intumescences on Poplar Leaves. I. Structure and Development

Carl D. La Rue
American Journal of Botany
Vol. 20, No. 1 (Jan., 1933), pp. 1-17
Stable URL: http://www.jstor.org/stable/2435992
Page Count: 17
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Intumescences on Poplar Leaves. I. Structure and Development
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Abstract

1. This paper reports the results of a study of the structure and development of intumescences on leaves of Populus grandidentata and P. tremuloides. 2. The intumescences develop rapidly on leaves confined in damp chambers, but are found in nature only on leaves which have been rolled or fastened together in pairs by insects. 3. Populus grandidentata and P. tremuloides are the only species of the genus which this study has shown to be capable of producing intumescences. Populus deltoides, P. balsamifera, P. alba, P. simonii, and P. nigra var. italica never produced intumescences under any of the conditions to which they were subjected. 4. Leaves of all ages, except those just ready to fall and those which have just emerged from the bud, are capable of developing intumescences. 5. The outgrowths occur on both laminae and petioles. On the laminae they appear on both upper and lower surfaces, but are most abundant on the lower surface. On either surface they are most abundant along the midribs and the larger veins. 6. The outgrowths are due to swelling of the cells, which are not increased in number. Therefore the abnormalities are to be considered hypertrophies. 7. The hypertrophied cells do not separate from one another, and no dissolution of any layers of the cell walls has been observed. 8. The leaves must be kept in damp chambers for three days before the outgrowths become apparent. 9. Under the conditions of these experiments, no periderm develops between the intumescences and the normal tissue of the leaves.

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