Gossypium arboreum (?) (var.  Nankin cotton) (Malvaceae).—­The cotyledons behave in nearly the same manner as those of the Anoda.  On June 15th the cotyledons of two seedlings were .65 inch in length (measured along the midrib) and stood horizontally at noon; at 10 P.M. they occupied the same position and had not fallen at all.  On June 23rd, the cotyledons of one of these seedlings were 1.1 inch in length, and by 10 P.M. they had fallen from a horizontal position to 62o beneath the horizon.  The cotyledons of the other seedling were 1.3 inch in length, and a minute true leaf had been formed; they had fallen at 10 P.M. to 70o beneath the horizon.  On June 25th, the true leaf of this latter seedling was .9 inch in length, and the cotyledons occupied nearly the same position at night.  By July 9th the cotyledons appeared very old and showed signs of withering; but they stood at noon almost horizontally, and at 10 P.M. hung down vertically.

Gossypium herbaceum.—­It is remarkable that the cotyledons of this species behave differently from those of the last.  They were observed during 6 weeks from their first development until they had grown to a very large size (still appearing fresh and green), viz. 2 ½ inches in breadth.  At this age a true leaf had been formed, which with its petiole was 2 inches long.  During the whole of these 6 weeks the cotyledons did not sink at night; yet when old their weight was considerable and they were borne by much elongated petioles.  Seedlings raised from some seed sent us from Naples, behaved in the same manner; as did those of a kind cultivated in Alabama and of the Sea-island cotton.  To what species these three latter forms belong we do not know.  We could not make out in the case of the Naples cotton, that the position of the cotyledons at night was influenced by the soil being more or less dry; care being taken that they were not rendered flaccid by being too dry.  The weight of the large cotyledons of the Alabama and Sea-island kinds caused them to hang somewhat downwards, when the pots in which they grew were left for a time upside down.  It should, however, be observed that these three kinds were raised in the middle of the winter, which sometimes greatly interferes with the proper nyctitropic movements of leaves and cotyledons. [page 304]

Cucurbitaceae.—­The cotyledons of Cucurbita aurantia and ovifera, and of Lagenaria vulgaris, stand from the 1st to the 3rd day of their life at about 60o above the horizon, and at night rise up so as to become vertical and in close contact with one another.  With Cucumis dudaim they stood at noon at 45o above the horizon, and closed at night.  The tips of the cotyledons of all these species are, however, reflexed, so that this part is fully exposed to the zenith at night; and this fact is opposed to the belief that the movement is of the same nature as that of sleeping plants.  After the first two or three days the cotyledons diverge more during the day and