60 
PROCEEDINGS OP THE PERTHSHIRE SOCIETY OP NATURAL SCIENCE. 
Conveyance by vjater is a far less general means than 
by wind, and special adaptations are rare. Of course, 
the seeds or fruits of any plants growing on the side 
of a stream may fall into it, and may be conveyed to 
a considerable distance, if light enough to float, be¬ 
fore being again cast on land. Of this mode of con¬ 
veyance we have clear proof in the occurrence of typi¬ 
cally alpine plants frequently here and there along our 
rivers in the lower grounds. But no special adaptations 
are needed or are met with for this method. Very few of 
our native plants live floating freely on the surface of the 
water, though in the tropics such plants are so abundant 
as to form floating islands, often over an acre in extent. 
The seeds of these plants germinate under water, and they 
are dispersed without special means by the movements of 
the plant freely on the surface of the water, carried along 
by winds or by currents. 
Special adaptations occur in the water-lilies, so com¬ 
monly to be found in Scottish lochs. The fruit in 
both the white and the yellow water - lilies contains 
several spaces ranged round a central column like the 
spaces between the spokes of a wheel. In these lie nume¬ 
rous seeds. In the yellow water-lilies ( Nuphar ) the outer 
coat of the fruits alone splits open when the seeds are ripe, 
and the inner layer enclosing each of the various divisions 
splits away containing the seeds, and also enough air to 
buoy up the whole on the surface, where it floats for a 
time driven about by winds or currents, till a hole forms 
in the wall, and seeds drop out and sink to the 
bottom of the loch. There they germinate in the mud. 
In the white water-lily ( Nymphcea ) the seeds are set free 
when the fruit splits; but each seed has a coat that has 
grown up from the funiculus or stalk loosely round it, so 
as to cover it, enclosing air enough to float the seed, and 
thus to allow of its conveyance to some distance. On the 
decay of this coat, and the escape of the air, the seed sinks 
to the bottom. 
Adaptations for conveyance attached to the bodies of ani¬ 
mals. —Sticky secretions very seldom form the means among 
our native plants; never, in fact, as regards the seeds them¬ 
selves, one might say, though the seeds of Linum and of a 
few other plants become sticky when moistened. The fruits 
of a few show a similar quality, and the ovary of Linncea 
borealis is said to be sticky when ripe by reason of gland 
hairs. In some Labiates, the calyx, which breaks away 
with the fruits, is sticky for the same reason. 
Prickles or hooks form by far the most frequent 
means for attaching the fruits to the bodies or limbs 
of animals. It may be said that no Scottish plants 
show structures of this kind on the seeds themselves; 
indeed, seeds so provided are rarely met with any¬ 
where. The surface of the ovary sometimes bears 
many small prickles (e.g., Ranunculus arvensis, Cynoglos- 
surn officinale), or, as in some exotic genera, it may bear 
one or more spines or hooks of considerable size. A well- 
known example is the fruit of the “ Wait-a-bit Thom ” of 
South Africa (Harpagophytum), with hooked branched 
spines an inch long, and very strong. These fruits are 
said to be very injurious to sheep through sticking in their 
wool, and irritating the skin when the sheep lie down on 
them. Many Scottish plants with inferior ovaries have 
the outer surface of the receptacle-tube covered closely with 
prickles (e.g., Carrot, Torilis, &c.), or small sharp hooks 
(e.g., Circcea, Galium aparine or Cleavers, Asperula, 
Sanicula, &c.), which form very efficient grasping organs. 
In others there is only a ring (or two or three rings) of 
hooks round the edge below the calyx (e.g., Aqrimonia). 
In the native species of Geum, the style elongates as the 
seed ripens. Near its middle there is an abrupt bend. 
When the seed is ripe the part of the style beyond this 
breaks away, leaving a sharp hook, which, though small, 
can take a Arm grasp. In a few exotic plants the corolla 
of the flower remains adherent to the top of the carpel, 
forming sharp hard hooks as in Tragoeceros, in which there 
are two such in the rayflowers. Such a modification of 
the corolla is not met with in any of our native plants. 
The flower-stalk seldom bears hooks or spines for grasping, 
but not rarely the bracts are so furnished. In the 
burdock ( Arctium Lappa) each of the narrow bracts that 
form the involucre ends in a small sharp hook. The 
whole head breaks away from the stalk, and very readily 
adheres to the fur or feathers of passing quadrupeds or 
birds, or to the clothes of passers-by. In some Umbelli- 
ferce the flowerhead or inflorescence breaks off and be¬ 
comes attached to passing animals by aid of small spines 
over the surface of the bracts. In many grasses (e.g., 
barley) the glumes or bracts end in long prickly awns, 
which form efficient organs of attachment. 
Fleshy fruits are, as a rule, specially suited for the disper¬ 
sion of the seeds by quadrupeds, or more generally by birds; 
and plants with fruits of this kind may frequently be found 
in situations such as to show that the seeds must have 
been brought from a distance. As previously mentioned, 
the fruits are swallowed; the seeds pass, but little, if at 
all, the worse, through the intestine, being protected 
usually in some way by their structure from injury 
in their passage, and when discharged they germinate 
as readily as, or in some cases even more readily 
than, if they had never been subjected to this treat¬ 
ment. The seeds suited for this mode of dispersion 
