We may feel sure that the lateral shoots whilst growing would exhibit the same movement if carefully observed.
* 'Comptes Rendus,' April 30th, 1877. Also a second notice published separately in Bourdeaux, Nov. 12th, 1877. [page 212]
(19.) Lilium auratum (Fam. Liliaceae).--The circumnutation
Fig. 83. Lilium auratum: circumnutation of a stem in darkness, traced on a horizontal glass, from 8 A.M. on March 14th to 8.35 A.M. on 16th. But it should be noted that our observations were interrupted between 6 P.M. on the 14th and 12.15 P.M. on the 15th, and the movements during this interval of 18 h. 15 m. are represented by a long broken line. Diagram reduced to half original scale.
of the stem of a plant 24 inches in height is represented in the above figure (Fig. 83).
Fig. 84. Cyperus alternifolius: circumnutation of stem, illuminated from above, traced on horizontal glass, from 9.45 A.M. March 9th to 9 P.M. on 10th. The stem grew so rapidly whilst being observed, that it was not possible to estimate how much its movements were magnified in the tracing.
(20.) Cyperus alternifolius (Fam. Cyperaceae.)--A glass [page 213] filament, with a bead at the end, was fixed across the summit of a young stem 10 inches in height, close beneath the crown of elongated leaves. On March 8th, between 12.20 and 7.20 P.M. the stem described an ellipse, open at one end. On the following day a new tracing was begun (Fig. 84), which plainly shows that the stem completed three irregular figures in the course of 35 h. 15 m.]
Concluding Remarks on the Circumnutation of Stems.--Any one who will inspect the diagrams now given, and will bear in mind the widely separated position of the plants described in the series,--remembering that we have good grounds for the belief that the hypocotyls and epicotyls of all seedlings circumnutate,--not forgetting the number of plants distributed in the most distinct families which climb by a similar movement,--will 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.