CERTAIN SEEDS BURY THEMSELVES ІМ THE GROUND. 165 
We have :—(1) seed more or less pointed, with a plume of hairs directed backwards 
(see fig. 8) ; (2) vertical awn twisting, when dried, into a right-handed screw ; (3) hori- 
zontal, non-twisting portion rotating, when wet, in the direction of the hands of a watch, 
and coming into the same straight line with the lower part of the awn when the untwist- 
ing is complete; (4) cells of the twisting part capable of independent torsion. 
With some difficulty I succeeded in observing the seed of Anemone montana bury itself 
almost completely during the process of becoming wet. I do not know whether it is сара- 
Ме of being buried deeper as it dries. Le Maout and Decaisne * figure the achene of 
Anemone pulsatilla as bent and twisted. Max Wichurat describes Clematis azurea as 
having the appendages to the carpels twisted. : 
GERANIACEA. 
I merely mention this family to point out the general resemblance presented by the 
coccus and awn in some of its members to the burying-mechanisms already described. 
Fig. 5 (a dry Pelargonium-coccus) shows the flat, ribbon-like awn twisted into a right- 
handed screw, the knee, the horizontal non-twisted portion, the pointed fruit, and the 
plume of grappling-hairs. 
It is undeniably true, as Hanstein points out, that the external surface contracts more 
strongly than the internal one in drying; but this does not account for the direction of 
torsion ; Г find that, as in the above-described awns, the cells are capable of independent 
torsion. | 
I have made no experiments on the burying-powers of the Сегапіасеғ, as these һауе 
been already described by Hanstein, Roux, and Asa Gray. 
When we find among organisms belonging to widely different groups a curious struc- 
tural mechanism, repeating itself and performing in each case the same function, we 
conclude that this function is an important one in the economy of the plant. Thus, for 
instance, the importance of the distribution of seeds is pointed out by the existence of 
burs in widely different orders, such as the Composite (Burdock), Rosaceze ( Geum), and 
Rubiaceæ (Galium aparine)—of plumes to enable the seed to fly on the wind in many 
Compositze, Аросупасеге, Onagraceze, &c. bs 
Now in the burying seeds which we have been considering we have a similar case, а 
given function performed by essentially similar mechanism in plants belonging to widely 
different orders; and we accordingly conclude that the power of thrusting themselves 
into the ground is of special service to the seeds under consideration. "Two theories 
suggest themselves. i 22 
(i.) My father has observed that certain seeds are almost incapable of germinating in 
the light, whereas they do soreadily in the dark. This fact suggested that the power of 
self-burial has been developed to remedy the injury which the incapacity of the seeds to 
germinate in the light must cause to the species. I therefore made a comparative trial to 
determine this point. A number of Stipa-seeds were placed in a vessel half filled with 
‘lor’s Scientifie Memoi 853, p. 302. 
* English Translation, р. 175. + Taylor's Scientific Memoirs, Aug. 1853, р. 30 
