amount of movement of the tip during the 25 h. was .75 inch.  Several stolons were laid on a flat surface of damp sand, in the same manner as with those of the strawberry.  The friction of the sand did not interfere with their circumnutation; nor could we detect any evidence of their being sensitive to contact.  In order to see how in a state of nature they would act, when encountering a stone or other obstacle on the ground, short pieces of smoked glass, an inch in height, were stuck upright into the sand in front of two thin lateral branches.  Their tips scratched the smoked surface in various directions; one made three upward and two downward lines, besides a nearly horizontal one; the other curled quite away from the glass; but ultimately both surmounted the glass and pursued their original course.  The apex of a third thick stolon swept up the glass in a curved line, recoiled and again came into contact with it; it then moved to the right, and after ascending, descended vertically; ultimately it passed round one end of the glass instead of over it.

Many long pins were next driven rather close together into the sand, so as to form a crowd in front of the same two thin lateral branches; but these easily wound their way through the crowd.  A thick stolon was much delayed in its passage; at one place it was forced to turn at right angles to its former course; at another place it could not pass through the pins, and the hinder part became bowed; it then curved upwards and passed through an opening between the upper part of some pins which happened to diverge; it then descended and finally emerged through the crowd.  This stolon was rendered permanently sinuous to a slight degree, and was thicker where sinuous than elsewhere, apparently from its longitudinal growth having been checked.

Cotyledon umbilicus (Crassulaceae).—­A plant growing in a pan [page 220] of damp moss had emitted 2 stolons, 22 and 20 inches in length.  One of these was supported, so that a length of 4 ½ inches projected in a straight and horizontal line, and the movement of the apex was traced.  The first dot was made at 9.10 A.M.;

Fig. 89.  Cotyledon umbilicus:  circumnutation of stolon, traced from 11.15 A.M.  Aug. 25th to 11 A.M. 27th.  Plant illuminated from above.  The terminal internode was .25 inch in length, the penultimate 2.25 and the third 3.0 inches in length.  Apex of stolon stood at a distance of 5.75 inches from the vertical glass; but it was not possible to ascertain how much the tracing was magnified, as it was not known how great a length of the internode circumnutated.

the terminal portion soon began to bend downwards and continued to do so until noon.  Therefore a straight line, very nearly as long as the whole figure here given (Fig. 89), was first traced on the glass; but the upper part of this line has not been copied in the diagram.  The curvature occurred in the middle [page 221] of the penultimate internode; and its chief seat was at the distance of 1 1/4 inch from the apex; it appeared due to the weight of the terminal portion, acting on the more flexible part of the internode, and not to geotropism.  The apex after thus sinking down from 9.10 A.M. to noon, moved a little to the left; it then rose up and circumnutated in a nearly vertical plane until 10.35 P.M.  On the following day (26th) it was ob-