felt the full influence of the light, and travelled towards it for the next 2 h. 30 m. in an almost straight line.  The tracing has not been given, as it was almost identical with that of Apios under similar circumstances (Fig. 170).  By noon it had bowed itself to its full extent; it then circumnutated about the same spot and described two ellipses; by 5 P.M. it had retreated considerably from the light, through the action of apogeotropism.  After some preliminary trials for ascertaining the right degree of obscurity, some seedlings were placed (Sept. 16th) before a north-east window, and light was admitted through an ordinary linen and three muslin blinds.  A pencil held close by the pot now cast a very faint shadow on a white card, pointing from the window.  In the evening, at 4.30 and again at 6 P.M., some of the blinds were removed.  In Fig. 174 we see the course pursued under these circumstances by a rather old and not very sensitive cotyledon, 1.9 inch in height, which became much bowed, but was never rectangularly bent towards the light.  From 11 A.M., when the sky became rather duller, until 6.30 P.M., the zigzagging was conspicuous, and evidently consisted of drawn-out ellipses.  After 6.30 P.M. and during the night, it retreated in a crooked line from the window.  Another and younger seedling moved during the same time much more quickly and to a much greater distance, in an only slightly zigzag line towards the light; by 11 A.M. it was bent almost rectangularly in this direction, and now circumnutated about the same place.

Tropaeolum majus.—­Some very young seedlings, bearing only two leaves, and therefore not as yet arrived at the climbing stage of growth, were first tried before a north-east window without any blind.  The epicotyls bowed themselves towards the light so rapidly that in little more than 3 h. their tips pointed rectangularly towards it.  The lines traced were either nearly straight or slightly zigzag; and in this latter case we see that a trace of circumnutation was retained even under the influence of a moderately bright light.  Twice whilst these epicotyls were bending towards the window, dots were made every 5 or 6 minutes, in order to detect any trace of lateral movement, but there was hardly any; and the lines formed by their junction were nearly straight, or only very slightly zigzag, as in the other parts of the figures.  After the epicotyls had bowed themselves to the full extent towards the light, ellipses of considerable size were described in the usual manner. [page 429]

After having seen how the epicotyls moved towards a moderately bright light, seedlings were placed at 7.48 A.M. (Sept. 7th) before a north-east window, covered by a towel, and shortly afterwards by an ordinary linen blind, but the epicotyls still moved towards the window.  At 9.13 A.M. two additional muslin blinds were suspended, so that the seedlings received very little more light from the window than from the interior of the room.  The sky varied in brightness, and the seedlings occasionally