118 
PLANT STUDIES 
FIG. 122. A fruit of witch 
hazel discharging its 
seeds. After BEAL. 
light or sandy soil (see Fig. 120). 
When the work of the season is over, 
and the absorbing rootlets have 
shriveled, the plant is easily blown 
from its anchorage by a gust of wind, 
and is trundled along the surface like 
a light wicker ball, the ripe seed ves- 
sels dropping their seeds by the way. 
In case of an obstruction, such as a 
fence, great masses of these tumble- 
weeds may often be seen lodged 
against the windward side. 
79. Discharge of spores. In many 
plants the distribution of spores and 
seeds is not provided for by any of 
the methods just mentioned, but the vessels containing 
them are so constructed that they are discharged with 
more or less violence and are some- 
what scattered. 
Many spore cases, especially those 
of the lower plants, burst irregularly, 
and with sufficient violence to throw 
out spores. In the liverworts pecu- 
liar cells, called elaters or "jumpers," 
are formed among the spores, and 
when the wall of the spore case is 
ruptured the elaters are liberated, 
and by their 'active motion assist in 
discharging the spores. 
In most of the true mosses the 
spore case opens by pushing off a 
lid at the apex, which exposes a 
delicate fringe of teeth covering the 
mouth of the urn-like case. These 
teeth bend in and out of the open 
spore case as they become moist or 
FIG. 123. A pod of wild bean 
bursting, the two valves 
violently twisting and dis- 
charging the seeds. After 
BEAL. 
