CERTAIN SEEDS BURY THEMSELVES IN THE GROUND. 163 
He also describes a method of progression by turning over and over, and a kind of 
creeping movement caused by the extension and flexion of the awns. Prof. Hildebrand 
suggests that possibly the more important function of the twisted and bent awns of 
- Avena and other grasses may be similar to that of Erodium, i. e. to bury the seeds in the 
ground. From analogy with Stipa, and from other considerations, there can be little doubt 
that this surmise is correct. | 
The fruit of Avena elatior, 6 times magnified, is given in fig. 4. Тһе vertical part of 
the awn (attached to the outer palea or flowering glume) is about 5 mm. in length, and 
is strongly twisted into a right-handed screw of about 4 turns. It follows that, justas in 
Stipa, the horizontal portion (6 mm. long) revolves in the direction of the hands of a watch 
when the awn is wetted. It is more sensitive hygroscopically than Stipa, and untwists 
very quickly (one turn in from 15” to 30”) when placed in water, as compared with the 
Stipa-hygroscope, which makes one revolution in 2 or 3 minutes. 
It will be seen that the point is blunt, and that it is covered with a plume of hairs 
pointing backwards as in Stipa; but these hairs seem to me too weak to be of much 
service. The horizontal portion of the awn is not feathered, but armed (as is also the 
twisting part) with minute reflexed barbs. I have not succeeded in observing the process 
of burial in Avena; nor has Hildebrand seen it. But I found that the seeds of a patch of 
wild oats growing in a ploughed field had succeeded in burying themselves. I believe 
that the mechanism of burial is not quite the same in Avena as in Stipa; the seed is too 
heavy to be held vertically, and the awn does not seem fitted for so supporting it. More- 
over the specimens which I found buried were not in a situation where low herbage could 
have entangled their awns, but among bare lumps of clay. I presume that the point is 
pushed laterally against inequalities in the ground, other projections being made use of as 
points d'appui. 
In explaining the mechanism of torsion in Avena, I am compelled, unfortunately, to 
differ entirely from Prof. Hildebrand. His view has been already mentioned. Against it 
I bring forward the arguments :— 
(i.) That it does not account for the direction of torsion being constantly the same. 
(ii.) That the surface which he believes to be the most contractile is on the conver 
side at the bending-point. 
(iii.) The strong argument that the cells, when isolated by nitric acid and chlorate of 
potassium, exhibit precisely the same power of independent torsion as those of the Stipa- 
awn. 
The mechanism of the knee is, I believe, the same in Avena as in Stipa. Professor 
Hildebrand figures a section of this awn (which is morphologically identical with that of 
Stipa) as having two cavities answering to the hollow ribs of Stipa, and, like them, filled 
with cells containing chlorophyl in the young state. In this condition the ribs make an 
“The following trick is made use of when any thing in a family is lost, to make the person suspected confess the 
fault and restore what is lost. Take a beard of wild oat while 'tis greenish, and twist it in the shape of a little cross, 
giving it to the person suspected, and whose guilt they are pretty well assured of. Give also to the rest of the family 
little crosses, but made of different stalks, as hay and wheat ; put all these in а cut apple, and the little wild oat will 
8row sensible of the moisture, untwisting itself and turning, to the great amazement of all the spectators.” 
