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movement towards the surface of the stem, without thedivergence between it and the uppermost leaf upon thehelix becoming diminished, until the leaf had arrived atthe lateral surface of the stem, and there become perma-nently fixed. It is equally clear that if the rest of theleaves should follow this first at uniform distances, fromthe turns of the spiral being closer towards the interior,the divergence between the successive leaves would in-crease in proportion as they were situated more internally,and would first acquire the dimension normal for thespecies at the transit of these leaves over on to the heliacalline. On the other side it is likewise evident that, with-out any alteration of their divergence, the leaves wouldseem to traverse a spiral, if each of them proceeded to-wards the periphery upon the radius on which it standsat its first origin ; for during the expansion of the axis ofthe bud, its most external part extends outwards andupwards to become the surface of the stem, the outerend of the spiral running upon this part of the axis,passes, as a continuation of the helix, on to the outersurface of the stem, and the succeeding leaf advances justso much nearer to the end of the spiral line, not becauseit makes a lateral movement upon it, but because thespiral line is abbreviated in the direction towards the leaf,and its point of transition into the helix advances nearerto the point at which the radius, on which the leaf stands,intersects the circumference of the stem. Which of theseprocesses occurs, whether the leaf actually advances late-rally, or the motion is only apparent, may be decided byinvestigation whether or not the divergence of the leavesalters. Now I believe that it will be found on examina-tion of the position of the leaves, that they exhibit thesame divergence in the terminal bud as on the stem, andthat the arrangement of the leaves passes with uniformdivergence from the helix into the spiral, and is continuedin this; while, according to Meneghini’s idea, the diver-gence must increase in the spiral. The distance froma leaf to its successor on the spiral will naturally be