The natural history of plants, their forms, growth, reproduction, and distribution; . not demonstrable with the same precision, areinstances in which one story shows twenty-one leaves which are connected by agenetic spiral with eight revolutions; and where a story includes thirty-fourleaves which are connected by a genetic spiral with thirteen revolutions. In theone case any two leaves next one another in age in a story are separated from one DISTRIBUTION OF THE GREEN LEAVES ON THE STEM. 401 another ^ of the circumference; in the other case by ^; and from this it follows that in the one instan
The natural history of plants, their forms, growth, reproduction, and distribution; . not demonstrable with the same precision, areinstances in which one story shows twenty-one leaves which are connected by agenetic spiral with eight revolutions; and where a story includes thirty-fourleaves which are connected by a genetic spiral with thirteen revolutions. In theone case any two leaves next one another in age in a story are separated from one DISTRIBUTION OF THE GREEN LEAVES ON THE STEM. 401 another ^ of the circumference; in the other case by ^; and from this it follows that in the one instance there are twenty-one, and in the other thirty-four orthostichies. If we place these actually-observed instances together, we have the series ^. S> 5> TS> ^T» s^- But the variety of the conditions on which the leaves are arranged is notI exhausted by a long way. Although but seldom, still cases have been observed which can be placed together in the series ^, ^, f, ^, -^^ , and also in the series hh-Ti-TS I^ ^11 these series this very remarkable peculiarity occurs, that. Fig. 100.—Plan of Five-thirteenths Phyllotaxis. in each individual fraction the denominator is equal to the sum of the denom-inators, and the numerator is equal to the sum of the numerators of the twopreceding fractions. Moreover it must be here particularly mentioned that the divergence, by whichthe leaves following one another in age are separated in a horizontal direction, isthe more difficult to establish the smaller it becomes. The one-third, two-fifths, andthree-eighths arrangements are the most easily demonstrable on the full-grownshoots, although occasionally doubt arises as to whether the three, five, and eightorthostichies represent completely straight lines. But the demonstration of ^ andthe ^ arrangements, especially in green herbaceous stems, is very difficult anduncertain. 402 DISTRIBUTION OF THE GREEN LEAVES ON THE STEM. There are only few plants on whose branches or axes several sto
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectbotany, bookyear1902
