Trifolium.—­The germination of 21 species was observed.  In most of them the cotyledons rise hardly at all, or only slightly, at night; but those of T. glomeratum, striatum and incarnactum rose from 45o to 55o above the horizon.  With T. subterraneum, leucanthemum and strictum, they stood up vertically; and with T. strictum the rising movement is accompanied, as we shall see, by another movement, which makes us believe that the rising is truly nyctitropic.  We did not carefully examine the cotyledons of all the species for a pulvinus, but this organ was distinctly present in those of T. subterraneum and strictum; whilst there was no trace of a pulvinus in some species, for instance, in T. resupinatum, the cotyledons of which do not rise at night.

Trifolium subterraneum.—­The blades of the cotyledons on the first day after germination (Nov. 21st) were not fully expanded, being inclined at about 35o above the horizon; at night they rose to about 75o.  Two days afterwards the blades at noon were horizontal, with the petioles highly inclined upwards; and it is remarkable that the nocturnal movement is almost wholly confined to the blades, being effected by the pulvinus at their bases; whilst the petioles retain day and night nearly the same inclination.  On this night (Nov. 23rd), and for some few succeeding nights, the blades rose from a horizontal into a vertical position, and then became bowed inwards at about an average angle of 10o; so that they had passed through an angle of 100o.  Their tips now almost touched one another, their bases being slightly divergent.  The two blades thus formed a highly inclined roof over the axis of the seedling.  This movement is the same as that of the terminal leaflet of the tripartite leaves of many species of Trifolium.  After an interval of 8 days (Nov. 29th) the blades were horizontal during the day, and vertical at night, and now they were no longer bowed inwards.  They continued to move in the same manner for the following two months, by which time they had increased greatly in size, their petioles being no less than .8 of an inch in length, and two true leaves had by this time been developed.

Trifolium strictum.—­On the first day after germination the cotyledons, which are provided with a pulvinus, stood at noon horizontally, and at night rose to only about 45o above the horizon.  Four days afterwards the seedlings were again observed at night, and now the blades stood vertically and were in contact, excepting the tips, which were much deflexed, so that they faced the zenith.  At this age the petioles are curved [page 310] upwards, and at night, when the bases of the blades are in contact, the two petioles together form a vertical ring surrounding the plumule.  The cotyledons continued to act in nearly the same manner for 8 or 10 days from the period of germination; but the petioles had by this time become straight and had increased much in length.  After from 12 to 14 days the first simple true leaf was formed, and during the ensuing fortnight a remarkable movement was repeatedly observed.  At I. (Fig. 125) we have a sketch, made in the middle of the day, of a seedling about a fortnight old.  The two cotyledons, of which Rc is the right and Lc the left one, stand directly opposite one another,