Abstract
TWO parts of the Journal of the Botanical Laboratory of the University of Pennsylvania recently oreceived (vol. iv., No. 2, and vol. v., No. i) contain a number of interesting papers. Dr. D. W. Steck-beck has studied the comparative histology and irritability of sensitive plants. The majority of the 'highly sensitive species are natives of subtropical arid tropical America, and their most widespread irritable response is the nyctitropic or “sleep-movement.” The author suggests that the phenomenon of propagation oof stimuli is centred in the endodermis, the cells of which contain a greater or less number of crystals of ooxalate of lime, the number, regularity of shape, and degree of restriction to the endodermis increasing with the increase of sensitivity shown by the plant; the climax is reached in the two highly sensitive plants Mimffsa pudica and Biophytum sensitivum. Each crystal is surrounded by a protoplasmic sac, threads from which pass through adjacent cell-membranes so as to form continuous protoplasmic connections throughout the endodermal tissue; the crystals with their protoplasmic connections are regarded as the special conducting lines for stimuli. The cells of the pulvinus of the leaves are found to contain aggregation bodies, resembling those described by Darwin and others, increasing in amount and complexity with increasing sensitiveness; these show contraction and aggregation changes under stimulation. They are proteinaceous in nature, and all contractile changes resulting from external stimuli seem to be due to changes primarily in the protoplasmic sac by which each is surrounded, secondly in the aggregation body itself, and finally in the amount of liquid these may absorb or give off.
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Botanical Papers from Pennsylvania. Nature 107, 764–765 (1921). https://doi.org/10.1038/107764a0
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DOI: https://doi.org/10.1038/107764a0