SOME UNIQUE EXAMPLES OF DISPERSION OF 
SEEDS AND: FRUITS? 
PROF. W. J. BEAL. 
In the driftwood stranded here and there along streams 
may often be found dry, three-celled fruits of the bladdernut 
an inch and a half in diameter, brown and light, tough and 
water-tight. The seeds are very hard and smooth, enabling 
them, if kept in the water, to remain uninjured for a long time. 
But the ability to float on the water is not its only means of 
dispersion. Many of the dry pods hang on until winter, rat- 
tling in the wind. On falling, a portion remain near the parent 
bush and are liable to be carried away the next time the creek 
overflows its banks ; others are moved by the wind, and perhaps 
again by the water, and still others may be drifted for long dis- 
tances, even on an up grade, if there chances to be snow on 
the ground. 
Here, among the rubbish in spring, are some shriveled wild 
grapes, which missed a golden opportunity of being eaten by 
certain birds which could not digest their bony seeds ; but they 
have in reserve another mode of transportation, not by wing 
of bird, but by floating on water. Clean grape seeds will sink 
at once, but when covered by the dry skin and pulp they float. 
In a similar manner the dry seeds of several dogwoods are 
often eaten by birds for the pulps, but if not eaten they behave 
after the manner of grapes with dry, wrinkled skins. 
Narrow-leaved dock is a prominent weed, and is especially at 
home along ditches and river bottoms. On the back of each 
dry persistent sepal is an ovoid, pithy or spongy tubercle, all 
of which are not exactly life-preservers, but they are the next 
thing to it. The naked achene sinks at once when free from 
everything else, but when encased in its dry calyx it floats on 
the water. 
1 Read before Section G, American Association for the Advancement of 
Science, Boston Meeting, August, 1898. 
