* ‘Hist.  Phys. des Plantes d’Europe,’ tom. ii. 1841, p. 106. [page 514]

upright flower-heads, arising from branches in all sorts of positions, on plants growing in a warm greenhouse, were marked with thread, and after 24 h. six of them were vertically dependent; these therefore had travelled through 180o in this time.  Ten were extended sub-horizontally, and these had moved through about 90o.  Three very young peduncles had as yet moved only a little downwards, but after an additional 24 h. were greatly inclined.

At the time when the flower-heads reach the ground, the younger imperfect flowers in the centre are still pressed closely together, and form a conical projection; whereas the perfect and imperfect flowers on the outside are upturned and closely surround the peduncle.  They are thus adapted to offer as little resistance, as the case admits of, in penetrating the ground, though the diameter of the flower-head is still considerable.  The means by which this penetration is effected will presently be described.  The flower-heads are able to bury themselves in common garden mould, and easily in sand or in fine sifted cinders packed rather closely.  The depth to which they penetrated, measured from the surface to the base of the head, was between 1/4 and ½ inch, but in one case rather above 0.6 inch.  With a plant kept in the house, a head partly buried itself in sand in 6 h.:  after 3 days only the tips of the reflexed calyces were visible, and after 6 days the whole had disappeared.  But with plants growing out of doors we believe, from casual observations, that they bury themselves in a much shorter time.

After the heads have buried themselves, the central aborted flowers increase considerably in length and rigidity, and become bleached.  They gradually curve, one after the other, upwards or towards the peduncle, in the same manner as did the perfect flowers at first.  In thus moving, the long claws on their summits carry with them some earth.  Hence a flower-head which has been buried for a sufficient time, forms a rather large ball, consisting of the aborted flowers, separated from one another by earth, and surrounding the little pods (the product of the perfect flowers) which lie close round the upper part of the peduncle.  The calyces of the perfect and imperfect flowers are clothed with simple and multicellular hairs, which have the power of absorption; for when placed in a weak solution of carbonate of ammonia (2 gr. to 1 oz. of water) their protoplasmic contents immediately became aggregated and afterwards displayed the usual slow movements.  This clover generally [page 515] grows in dry soil, but whether the power of absorption by the hairs on the buried flower-heads is of any importance to them we do not know.  Only a few of the flower-heads, which from their position are not able to reach the ground and bury themselves, yield seeds; whereas the buried ones never failed, as far as we observed, to produce as many seeds as there had been perfect flowers.