probably admit that the growing stems of all plants, if carefully observed, would be found to circumnutate to a greater or less extent.  When we treat of the sleep and other movements of plants, many other cases of circumnutating stems will be incidentally given.  In looking at the diagrams, we should remember that the stems were always growing, so that in each case the circumnutating apex as it rose will have described a spire of some kind.  The dots were made on the glasses generally at intervals of an hour, or hour and a half, and were then joined by straight lines.  If they had been made at intervals of 2 or 3 minutes, the lines would have been more curvilinear, as in the case of the tracks left on the smoked glass-plates by the tips of the circumnutating radicles of seedling plants.  The diagrams generally approach in form to a succession of more or less irregular ellipses or ovals, with their longer axes directed to different points of the compass during the same day or on succeeding days.  The stems there-[page 214] fore, sooner or later, bend to all sides; but after a stem has bent in any one direction, it commonly bends back at first in nearly, though not quite, the opposite direction; and this gives the tendency to the formation of ellipses, which are generally narrow, but not so narrow as those described by stolons and leaves.  On the other hand, the figures sometimes approach in shape to circles.  Whatever the figure may be, the course pursued is often interrupted by zigzags, small triangles, loops, or ellipses.  A stem may describe a single large ellipse one day, and two on the next.  With different plants the complexity, rate, and amount of movement differ much.  The stems, for instance, of Iberis and Azalea described only a single large ellipse in 24 h.; whereas those of the Deutzia made four or five deep zigzags or narrow ellipses in 11 ½ h., and those of the Trifolium three triangular or quadrilateral figures in 7 h.

Circumnutation of stolons or runners.

Stolons consist of much elongated, flexible branches, which run along the surface of the ground and form roots at a distance from the parent-plant.  They are therefore of the same homological nature as stems; and the three following cases may be added to the twenty previously given cases.

[Fragaria (cultivated garden var.):  Rosaceae.—­A plant growing in a pot had emitted a long stolon; this was supported by a stick, so that it projected for the length of several inches horizontally.  A glass filament bearing two minute triangles of paper was affixed to the terminal bud, which was a little upturned; and its movements were traced during 21 h., as shown in Fig. 85.  In the course of the first 12 h. it moved twice up and twice down in somewhat zigzag lines, and no doubt travelled in the same manner during the night.  On the following [page 215] morning after an interval of 20 h. the apex stood a little higher than it did at first, and this shows that the stolon had not been Fig. 85.  Fragaria:  circumnutation of stolon, kept in darkness, traced on vertical glass, from 10.45 A.M.  May 18th to 7.45 A.M. on 19th.