816 Means of Plant Dispersion. [ August, 
and awns. The grain of Stipa is scattered around the plant by 
the wind, the long awn, aiding in this as well as in directing it, 
point downward, like a dart to the earth, and pushes the back- 
wardly roughened point into the sand, the grain boring its way 
in as the awn twists and untwists according to varying conditions 
of moisture. 
Seeds also possess contrivances for dispersion analogous to 
those already described for fruits. There are seeds with wings, 
with tufts of-hairs at the end, with cottony fibers imbedding 
them. 
Some of the best examples of winged seeds are found in the 
Coniferz, particularly the pine and fir. The seeds of these, either 
singly or in twos, are attached to the inner sides of the scales of 
- the cones, which, when ripe, open so that the seeds may easily 
fall out or be detached by the wind. The Bignonia family has 
good representatives of this mode. When the pod of the catalpa 
opens, winged seeds are found, the wings being cut into a fringe. 
Bignonia capreolata and Tecoma radicans, the latter common in 
cultivation as the trumpet-creeper, are also provided with winged 
seeds. In some of the smaller plants, as in species of Arabis (4. 
levigata and A. canadensis) the little seeds have a broad wing 
that materially helps their dispersion when the pod dehisces. 
The analogues of fruit with pappus are seeds with a coma, oF 
tuft of hairs. Some of the best illustrations are those of Ascle- 
pias and Apocynum. The silky down of the seeds of the silk- 
weed, or milk-weed (Asclepias) forms as efficient a means 
spreading by wind agency as the hairs of the thistle or dandelion. 
The hairs are fully developed as soon as the pod is ripe and 
ready to open, and are so closely packed that on its opening 
they bulge out in a fluffy mass like those in the boll of the a 
ton plant, also a good example of a similar provision. 
seeds of Asclepias are also very flat and margined, so as = 
come under the head of those furnished with a wing, being thus 
doubly provided with wind adaptations, The willow-herbs (Ep 
lobium) also have seeds with a tuft of hair at the end. The mos 
common and showy of these, Epilobium angustifolium, often 
called fire-weed from its habit of springing up from ground a 
cently burnt over by fire, is thus able to spread with rapidity, ike 
its congener, Evechthites hieracifolia, of the Composite, also cal 
fire-weed from the same habit. 
