action of light; and if any enters even temporarily on one side, they merely bend to this side in slightly zigzag lines.  Of the three tracings one alone (Fig. 49) is here given.  Had the observations been more frequent during the 12 h. two oval figures would have been described with their longer axes at right angles to one another.  The actual amount of movement of the apex from side to side was about .3 of an inch.  The figures described by the other two seedlings resembled to a certain extent the one here given.

Fig. 49.  Phalaris Canariensis:  circumnutation of a cotyledon, with a mark placed below the apex, traced on a horizontal glass, from 8.35 A.M.  Nov. 26th to 8.45 A.M. 27th.  Movement of apex magnified 7 times, here reduced to one-half scale.

A seedling which had just broken through the ground and projected only 1/20th of an inch above the surface, was next observed in the same manner as before.  It was necessary to clear away the earth all round the seedling to a little depth in order to place a mark beneath the apex.  The figure (Fig. 50) shows that the apex moved to one side, but changed its course ten times in the course of the ten hours of observation; so that there can be no doubt about its circumnutation.  The cause of the general movement in one direction could hardly be attributed to the entrance of lateral light, as this was carefully guarded against; and we suppose it was in some manner connected with the removal of the earth round the little seedling.

Fig. 50.  Phalaris Canariensis:  circumnutation of a very young cotyledon, with a mark placed below the apex, traced on a horizontal glass, from 11.37 A.M. to 9.30 P.M.  Dec. 13th.  Movement of apex greatly magnified, here reduced to one-fourth of original scale.

Lastly, the soil in the same pot was searched with the aid of a lens, and the white knife-like apex of a seedling was found on an exact level with that of the surrounding surface.  The soil was removed all round the apex to the depth of a quarter of an inch, the seed itself remaining covered.  The pot, protected from lateral light, was placed under the micro-[page 64] scope with a micrometer eye-piece, so arranged that each division equalled 1/500th of an inch.  After an interval of 30 m. the apex was observed, and it was seen to cross a little obliquely two divisions of the micrometer in 9 m. 15 s.; and after a few minutes it crossed the same space in 8 m. 50s.  The seedling was again observed after an interval of three-quarters of an hour, and now the apex crossed rather obliquely two divisions in 10 m.  We may therefore conclude that it was travelling at about the rate of 1/50th of an inch in 45 minutes.  We may also conclude from these and the previous observations, that the seedlings of Phalaris in breaking through the surface of the soil circumnutate as much as the surrounding pressure will permit.  This fact accounts (as in the case before given of the asparagus) for a circular, narrow, open space or crack being distinctly visible round several seedlings which had risen through very fine argillaceous sand, kept uniformly damp.